What separates a vector quantity from a scalar quantity?

A vector has magnitude and direction; a scalar has magnitude only. Velocity is a vector, while speed is a scalar.

When is the point-object model useful in kinematics?

When an object's size and rotation do not matter for the motion being studied. Its position can then represent the whole object.

When may the constant-acceleration kinematic equations be used?

Only over an interval with constant acceleration. They are not general formulas for changing acceleration.

Why must a velocity statement name or imply a reference frame?

Velocity depends on the observer's frame. The same object can be at rest in one frame and moving in another.

Why can horizontal and vertical projectile motion be analyzed separately?

Perpendicular components evolve independently. With negligible air resistance, gravity changes only the vertical component.

Can an object have zero velocity and nonzero acceleration at one instant?

Yes. At the top of a vertical toss, velocity is momentarily zero while gravitational acceleration still points downward.

A runner completes one lap and returns to the start. How do distance and displacement compare?

The distance is one lap, while the displacement is zero. Displacement depends only on the change from initial to final position.

What makes a reference frame convenient for a motion problem?

It makes the relevant positions or velocities simple. A good frame reduces bookkeeping without changing physical predictions.

How are the components of a launch velocity v at angle θ found?

v_x = v cos θ and v_y = v sin θ. The angle is measured from the positive horizontal axis.

What does average velocity measure?

Displacement per elapsed time. In one dimension, v_avg = Δx/Δt; direction comes from the sign of Δx.

Do a vector's magnitude and its component use different SI units?

No. A vector and each of its components use the same unit; for example, velocity and its x-component both use m/s.

A velocity-versus-time graph curves upward and becomes progressively steeper while staying above zero. What does that show?

The object moves in the positive direction and speeds up with increasing positive acceleration. The graph's slope is acceleration; because that slope changes, the acceleration is nonuniform.

What are a projectile's horizontal and vertical accelerations when air resistance is negligible and up is positive?

a_x = 0 and a_y = -g. Horizontal velocity stays constant while vertical velocity changes.

What does average acceleration measure?

Change in velocity per elapsed time. In one dimension, a_avg = Δv/Δt.

What does a negative one-dimensional vector component mean?

It points opposite the chosen positive direction. The minus sign describes direction, not a negative physical size.

For constant acceleration, what does v = v₀ + at retrieve?

Velocity after elapsed time t. Use it when initial velocity, constant acceleration, and time are known or related.

How are a vector's magnitude and direction reconstructed from perpendicular components v_x and v_y?

v = √(v_x² + v_y²). When v_x ≠ 0, use θ = tan⁻¹(v_y/v_x) and the component signs to choose the quadrant. If v_x = 0 and v_y ≠ 0, the vector points along +y or -y; if both components are zero, its direction is undefined.

At an instant when velocity is nonzero, how do velocity and acceleration signs show whether a one-dimensional object is speeding up?

It speeds up when velocity and acceleration have the same sign. Opposite signs mean speed is decreasing at that instant.

What does the slope of a position-versus-time graph represent?

Velocity. A steeper slope means a larger speed, and the slope's sign gives direction.

Two observers use inertial frames, where an object with zero net force has constant velocity. If the observers move at constant velocity relative to each other, do they agree on an object's acceleration?

Yes, in a Galilean inertial-frame model. Subtracting a constant frame velocity changes velocity but not acceleration. This definition distinguishes an inertial frame from an accelerating, noninertial frame.

A projectile lands at its launch height with negligible air resistance. How do its launch and landing speeds compare?

They are equal. The horizontal component is unchanged, and the vertical component returns with equal magnitude and opposite sign.

A car's velocity changes from -2 m/s to +6 m/s in 2 s. What is its average acceleration?

+4 m/s². Δv = 8 m/s, and 8 m/s ÷ 2 s = 4 m/s².

If the positive axis is reversed, what happens to a one-dimensional vector component and its magnitude?

The component changes sign, while the magnitude stays the same. A coordinate choice changes the signed description, not the physical vector.

For constant acceleration, what does Δx = v₀t + ½at² retrieve?

Displacement over time t. It includes both initial-velocity motion and the displacement added by constant acceleration.

For a horizontal launch from height h in uniform gravity with negligible air resistance, what sets the time to reach the ground?

The vertical drop alone. Starting with v_y = 0, the time follows h = ½gt² and does not depend on horizontal speed.

Why can average speed differ from the magnitude of average velocity?

Average speed uses total distance, while average velocity uses displacement. Reversing direction increases distance without necessarily increasing displacement.

What does the slope of a velocity-versus-time graph represent?

Acceleration. The slope's units are (m/s)/s = m/s².

A passenger walks forward at 2 m/s inside a train moving forward at 18 m/s. What is the passenger's ground velocity?

20 m/s forward. Add the passenger's train-relative velocity to the train's ground velocity.

Does projectile mass affect the ideal trajectory when air resistance is negligible?

No. All projectiles have the same gravitational acceleration, so equal initial conditions give equal trajectories.

Can an object have nonzero velocity and zero acceleration?

Yes. Constant-velocity motion has nonzero velocity while the velocity change, and therefore acceleration, is zero.

A cart starts from rest with constant acceleration. Which graph should be linear if x = x₀ + ½at² applies?

Position x versus t². Its slope is ½a when the initial velocity is zero.

What does signed area under a velocity-versus-time graph represent?

Displacement. Area below the time axis contributes negative displacement.

At the highest point of a projectile's path, what are its vertical velocity and vertical acceleration?

v_y = 0, but a_y = -g. The vertical velocity pauses before reversing; gravity does not switch off.

How can a motion sensor test whether a cart moves at constant velocity?

Record position at equal time intervals and graph position versus time. A straight line with nearly constant slope supports constant velocity.

A car passes a parked observer at 12 m/s. What is the parked observer's velocity in the car's frame?

-12 m/s. In the car's frame, the ground and observer move backward at the car's speed.

Which constant-acceleration equation connects speed and displacement without using time?

v² = v₀² + 2aΔx. Use signed one-dimensional quantities and constant acceleration.

How could video data test the independence of projectile components?

Track x and y at equal times. A linear x-versus-t graph and a quadratic vertical trend support constant horizontal velocity and vertical acceleration.

A velocity-versus-time graph stays below zero but slopes upward toward zero. What is happening?

The object moves in the negative direction while slowing down. Velocity is negative and acceleration is positive.

How can average velocity over a very short interval approximate instantaneous velocity?

Shrink the time interval around the instant. The displacement divided by that short interval approaches the local position–time graph slope.

A walker moves 7 m east, then 3 m west. What is the one-dimensional displacement if east is positive?

+4 m. Add signed displacements: +7 m + (-3 m) = +4 m.

What shape is the path of a projectile with a nonzero horizontal velocity component in a uniform gravitational field when air resistance is negligible?

A parabola. Constant horizontal velocity and constant vertical acceleration produce the curve. A purely vertical launch is the special case: its spatial path is a vertical line.

In a motion diagram with dots at equal time intervals and velocity arrows, what do wider dot spacing and longer arrows show?

Greater speed. Wider spacing means more distance is covered during each equal time interval, while longer velocity arrows represent a larger velocity magnitude. Each arrow points in the direction of motion.

What does signed area under an acceleration-versus-time graph represent?

Change in velocity. Add that signed area to the initial velocity to find the final velocity.

How is one-dimensional relative velocity calculated for two objects A and B?

v_A relative to B = v_A - v_B. Both velocities must be measured in the same frame before subtracting.

When its speed is nonzero, what direction does a projectile's instantaneous velocity point?

Tangent to its path. Its horizontal and vertical velocity components combine to set that direction.

What does choosing a system boundary decide in a mechanics problem?

It decides which objects belong to the system and which forces count as external. Internal interactions occur between objects inside the boundary.

What belongs on a free-body diagram for one chosen object?

Only forces exerted on that object by other objects. Do not draw velocity, acceleration, or forces the chosen object exerts elsewhere.

What assumptions define the ideal-string model used in introductory algebra-based physics?

The string is massless, inextensible, and flexible. It pulls along its length, doesn't stretch, and can redirect around an ideal pulley.

What does translational equilibrium require?

Zero net force. The object may be at rest or move with constant velocity.

In an inertial frame, how does Newton's second law connect force and motion?

ΣF = ma. The net external force on the chosen object or system causes its acceleration; mass sets how strongly the velocity responds.

How do mass and weight differ?

Mass measures inertia in kilograms; weight is gravitational force in newtons. Near a surface, F_g = mg.

Algebra-Based Physics 1 Flashcards: Complete 8-Unit Course Review

A 400-card review of concepts, formulas, graphs, experiments, and reasoning across eight units of algebra-based physics.

作者 Flashcards Open Source App

关于这套卡组

This 400-card deck reviews concepts, formulas, graphs, experiments, and reasoning across eight units of algebra-based physics. It moves through Kinematics; Force and Translational Dynamics; Work, Energy, and Power; Linear Momentum; Torque and Rotational Dynamics; Energy and Momentum of Rotating Systems; Oscillations; and Fluids.

What you'll retrieve

Choose the governing principle for a situation or claim, then explain the prediction in plain language.
Recall what a quantity or equation means, when it applies, how it scales, and which SI unit it uses.
Read slopes, signed areas, extrema, signs, and shapes across motion, force, energy, momentum, rotation, oscillation, and fluid graphs.
Plan a small experiment by naming useful variables, measurements, controls, linearized graphs, slope meanings, and uncertainty checks.
Solve one focused original algebra-based setup with units and a short reason.
Use selected reverse and contrast prompts to recognize conditions and separate common confusion pairs. The deck doesn't mechanically reverse every fact.

Bare formula-to-symbol lists, long multipart calculations, and imitation exam questions are excluded. The deck also stays outside calculus-based mechanics, three-dimensional angular-momentum analysis, electricity and magnetism, circuits, thermodynamics, waves and optics, modern physics, viscous-flow effects and nonideal viscosity corrections, turbulence, surface tension, and other topics beyond this algebra-based scope.

The order is deliberate: Units 1–4 establish motion, forces, energy, and momentum; Units 5–6 reuse those ideas for rotation and orbits; Unit 7 applies them to oscillations; Unit 8 closes with static and moving ideal fluids. Its release-direction cards ask only for the immediate acceleration in a static, uniform ideal fluid when weight and buoyancy are the only forces. Definitions appear before dependent uses. The sequence interleaves closely related formula, graph, condition, calculation, and contrast prompts with unrelated retrievals. Short prerequisite steps stay closer only when each card introduces a genuinely different idea.

Every prompt, answer, numerical setup, explanation, ordering choice, and metadata field was independently written from common physics knowledge and checked with compatible or authoritative fact sources. The CC0 label applies to that original expression and organization to the extent applicable rights exist; it does not claim ownership of common physics facts or third-party material.

This is an independently authored, unofficial educational deck by Flashcards Open Source App. It is not affiliated with or endorsed by any course or exam provider. No exam questions, mark schemes, curriculum prose, commercial deck text, source prose, logos, figures, or trade dress were copied.

这套卡组中的卡片

卡片 1
问题
What separates a vector quantity from a scalar quantity?
答案
A vector has magnitude and direction; a scalar has magnitude only. Velocity is a vector, while speed is a scalar.
卡片 2
问题
When is the point-object model useful in kinematics?
答案
When an object's size and rotation do not matter for the motion being studied. Its position can then represent the whole object.
卡片 3
问题
When may the constant-acceleration kinematic equations be used?
答案
Only over an interval with constant acceleration. They are not general formulas for changing acceleration.
卡片 4
问题
Why must a velocity statement name or imply a reference frame?
答案
Velocity depends on the observer's frame. The same object can be at rest in one frame and moving in another.
卡片 5
问题
Why can horizontal and vertical projectile motion be analyzed separately?
答案
Perpendicular components evolve independently. With negligible air resistance, gravity changes only the vertical component.
卡片 6
问题
Can an object have zero velocity and nonzero acceleration at one instant?
答案
Yes. At the top of a vertical toss, velocity is momentarily zero while gravitational acceleration still points downward.
卡片 7
问题
A runner completes one lap and returns to the start. How do distance and displacement compare?
答案
The distance is one lap, while the displacement is zero. Displacement depends only on the change from initial to final position.
卡片 8
问题
What makes a reference frame convenient for a motion problem?
答案
It makes the relevant positions or velocities simple. A good frame reduces bookkeeping without changing physical predictions.
卡片 9
问题
How are the components of a launch velocity v at angle θ found?
答案
v_x = v cos θ and v_y = v sin θ. The angle is measured from the positive horizontal axis.
卡片 10
问题
What does average velocity measure?
答案
Displacement per elapsed time. In one dimension, v_avg = Δx/Δt; direction comes from the sign of Δx.
卡片 11
问题
Do a vector's magnitude and its component use different SI units?
答案
No. A vector and each of its components use the same unit; for example, velocity and its x-component both use m/s.
卡片 12
问题
A velocity-versus-time graph curves upward and becomes progressively steeper while staying above zero. What does that show?
答案
The object moves in the positive direction and speeds up with increasing positive acceleration. The graph's slope is acceleration; because that slope changes, the acceleration is nonuniform.
卡片 13
问题
What are a projectile's horizontal and vertical accelerations when air resistance is negligible and up is positive?
答案
a_x = 0 and a_y = -g. Horizontal velocity stays constant while vertical velocity changes.
卡片 14
问题
What does average acceleration measure?
答案
Change in velocity per elapsed time. In one dimension, a_avg = Δv/Δt.
卡片 15
问题
What does a negative one-dimensional vector component mean?
答案
It points opposite the chosen positive direction. The minus sign describes direction, not a negative physical size.
卡片 16
问题
For constant acceleration, what does v = v₀ + at retrieve?
答案
Velocity after elapsed time t. Use it when initial velocity, constant acceleration, and time are known or related.
卡片 17
问题
How are a vector's magnitude and direction reconstructed from perpendicular components v_x and v_y?
答案
v = √(v_x² + v_y²). When v_x ≠ 0, use θ = tan⁻¹(v_y/v_x) and the component signs to choose the quadrant. If v_x = 0 and v_y ≠ 0, the vector points along +y or -y; if both components are zero, its direction is undefined.
卡片 18
问题
At an instant when velocity is nonzero, how do velocity and acceleration signs show whether a one-dimensional object is speeding up?
答案
It speeds up when velocity and acceleration have the same sign. Opposite signs mean speed is decreasing at that instant.
卡片 19
问题
What does the slope of a position-versus-time graph represent?
答案
Velocity. A steeper slope means a larger speed, and the slope's sign gives direction.
卡片 20
问题
Two observers use inertial frames, where an object with zero net force has constant velocity. If the observers move at constant velocity relative to each other, do they agree on an object's acceleration?
答案
Yes, in a Galilean inertial-frame model. Subtracting a constant frame velocity changes velocity but not acceleration. This definition distinguishes an inertial frame from an accelerating, noninertial frame.
卡片 21
问题
A projectile lands at its launch height with negligible air resistance. How do its launch and landing speeds compare?
答案
They are equal. The horizontal component is unchanged, and the vertical component returns with equal magnitude and opposite sign.
卡片 22
问题
A car's velocity changes from -2 m/s to +6 m/s in 2 s. What is its average acceleration?
答案
+4 m/s². Δv = 8 m/s, and 8 m/s ÷ 2 s = 4 m/s².
卡片 23
问题
If the positive axis is reversed, what happens to a one-dimensional vector component and its magnitude?
答案
The component changes sign, while the magnitude stays the same. A coordinate choice changes the signed description, not the physical vector.
卡片 24
问题
For constant acceleration, what does Δx = v₀t + ½at² retrieve?
答案
Displacement over time t. It includes both initial-velocity motion and the displacement added by constant acceleration.
卡片 25
问题
For a horizontal launch from height h in uniform gravity with negligible air resistance, what sets the time to reach the ground?
答案
The vertical drop alone. Starting with v_y = 0, the time follows h = ½gt² and does not depend on horizontal speed.
卡片 26
问题
Why can average speed differ from the magnitude of average velocity?
答案
Average speed uses total distance, while average velocity uses displacement. Reversing direction increases distance without necessarily increasing displacement.
卡片 27
问题
What does the slope of a velocity-versus-time graph represent?
答案
Acceleration. The slope's units are (m/s)/s = m/s².
卡片 28
问题
A passenger walks forward at 2 m/s inside a train moving forward at 18 m/s. What is the passenger's ground velocity?
答案
20 m/s forward. Add the passenger's train-relative velocity to the train's ground velocity.
卡片 29
问题
Does projectile mass affect the ideal trajectory when air resistance is negligible?
答案
No. All projectiles have the same gravitational acceleration, so equal initial conditions give equal trajectories.
卡片 30
问题
Can an object have nonzero velocity and zero acceleration?
答案
Yes. Constant-velocity motion has nonzero velocity while the velocity change, and therefore acceleration, is zero.
卡片 31
问题
A cart starts from rest with constant acceleration. Which graph should be linear if x = x₀ + ½at² applies?
答案
Position x versus t². Its slope is ½a when the initial velocity is zero.
卡片 32
问题
What does signed area under a velocity-versus-time graph represent?
答案
Displacement. Area below the time axis contributes negative displacement.
卡片 33
问题
At the highest point of a projectile's path, what are its vertical velocity and vertical acceleration?
答案
v_y = 0, but a_y = -g. The vertical velocity pauses before reversing; gravity does not switch off.
卡片 34
问题
How can a motion sensor test whether a cart moves at constant velocity?
答案
Record position at equal time intervals and graph position versus time. A straight line with nearly constant slope supports constant velocity.
卡片 35
问题
A car passes a parked observer at 12 m/s. What is the parked observer's velocity in the car's frame?
答案
-12 m/s. In the car's frame, the ground and observer move backward at the car's speed.
卡片 36
问题
Which constant-acceleration equation connects speed and displacement without using time?
答案
v² = v₀² + 2aΔx. Use signed one-dimensional quantities and constant acceleration.
卡片 37
问题
How could video data test the independence of projectile components?
答案
Track x and y at equal times. A linear x-versus-t graph and a quadratic vertical trend support constant horizontal velocity and vertical acceleration.
卡片 38
问题
A velocity-versus-time graph stays below zero but slopes upward toward zero. What is happening?
答案
The object moves in the negative direction while slowing down. Velocity is negative and acceleration is positive.
卡片 39
问题
How can average velocity over a very short interval approximate instantaneous velocity?
答案
Shrink the time interval around the instant. The displacement divided by that short interval approaches the local position–time graph slope.
卡片 40
问题
A walker moves 7 m east, then 3 m west. What is the one-dimensional displacement if east is positive?
答案
+4 m. Add signed displacements: +7 m + (-3 m) = +4 m.
卡片 41
问题
What shape is the path of a projectile with a nonzero horizontal velocity component in a uniform gravitational field when air resistance is negligible?
答案
A parabola. Constant horizontal velocity and constant vertical acceleration produce the curve. A purely vertical launch is the special case: its spatial path is a vertical line.
卡片 42
问题
In a motion diagram with dots at equal time intervals and velocity arrows, what do wider dot spacing and longer arrows show?
答案
Greater speed. Wider spacing means more distance is covered during each equal time interval, while longer velocity arrows represent a larger velocity magnitude. Each arrow points in the direction of motion.
卡片 43
问题
What does signed area under an acceleration-versus-time graph represent?
答案
Change in velocity. Add that signed area to the initial velocity to find the final velocity.
卡片 44
问题
How is one-dimensional relative velocity calculated for two objects A and B?
答案
v_A relative to B = v_A - v_B. Both velocities must be measured in the same frame before subtracting.
卡片 45
问题
When its speed is nonzero, what direction does a projectile's instantaneous velocity point?
答案
Tangent to its path. Its horizontal and vertical velocity components combine to set that direction.
卡片 46
问题
What does choosing a system boundary decide in a mechanics problem?
答案
It decides which objects belong to the system and which forces count as external. Internal interactions occur between objects inside the boundary.
卡片 47
问题
What belongs on a free-body diagram for one chosen object?
答案
Only forces exerted on that object by other objects. Do not draw velocity, acceleration, or forces the chosen object exerts elsewhere.
卡片 48
问题
What assumptions define the ideal-string model used in introductory algebra-based physics?
答案
The string is massless, inextensible, and flexible. It pulls along its length, doesn't stretch, and can redirect around an ideal pulley.
卡片 49
问题
What does translational equilibrium require?
答案
Zero net force. The object may be at rest or move with constant velocity.
卡片 50
问题
In an inertial frame, how does Newton's second law connect force and motion?
答案
ΣF = ma. The net external force on the chosen object or system causes its acceleration; mass sets how strongly the velocity responds.
卡片 51
问题
How do mass and weight differ?
答案
Mass measures inertia in kilograms; weight is gravitational force in newtons. Near a surface, F_g = mg.
卡片 52
问题
How does static friction choose its magnitude before slipping begins?
答案
It matches the needed tangential contact force up to a maximum. In general, f_s ≤ μ_sN.
卡片 53
问题
For an ideal spring in its linear range, what is the spring force when its end is displaced by a signed amount x from the relaxed or natural length?
答案
F_s = -kx. The sign shows that the spring force opposes the signed extension or compression and points toward the relaxed or natural length.
卡片 54
问题
What direction does centripetal acceleration point in circular motion?
答案
Toward the circle's center. It changes the velocity's direction even when speed is constant.
卡片 55
问题
What is the gravitational force magnitude between two point masses?
答案
F_g = Gm₁m₂/r². Here r is the center-to-center separation.
卡片 56
问题
Why isn't the normal force always equal to an object's weight?
答案
It adjusts to the contact and acceleration conditions. Other vertical forces or vertical acceleration can change its magnitude.
卡片 57
问题
What determines a friction coefficient in the simple model?
答案
The pair of contacting materials and their surface condition. It isn't a universal property of either material alone.
卡片 58
问题
What is the centripetal-acceleration magnitude for speed v and radius r?
答案
a_c = v²/r. It is a kinematic requirement, not a separate force.
卡片 59
问题
An elevator accelerates upward. How does the scale reading compare with a rider's weight?
答案
It is greater than the weight. Upward net force requires N - mg > 0.
卡片 60
问题
What does a spring constant k measure, and what is its SI unit?
答案
It measures stiffness in N/m. A larger k means more force is needed for the same displacement in the linear range.
卡片 61
问题
Three equal point masses are at (0,0), (3 m,0), and (0,3 m). Where is their center of mass?
答案
At (1 m,1 m). Average the x-coordinates and y-coordinates separately for equal masses.
卡片 62
问题
What provides centripetal force?
答案
The inward component of real forces such as tension, gravity, friction, or a normal force. 'Centripetal force' names their net inward result.
卡片 63
问题
How is near-surface gravitational field strength related to weight?
答案
F_g = mg. The local field strength g has units N/kg, equivalent to m/s².
卡片 64
问题
How is weight resolved on an incline of angle θ measured from horizontal?
答案
mg sin θ points down the slope and mg cos θ points into the slope. These are components of one gravitational force.
卡片 65
问题
What does Newton's third law say about an interaction between objects A and B?
答案
The force of A on B and the force of B on A have equal magnitude and opposite direction. They act on different objects.
卡片 66
问题
What does signed tangential acceleration describe during circular motion?
答案
It describes how quickly speed changes and which way the tangential acceleration points along the chosen tangent. Its magnitude is the absolute value of the instantaneous rate of change of speed. If it points with the velocity, speed increases; if it points against the velocity, speed decreases. Its sign follows the chosen tangent.
卡片 67
问题
What happens to gravitational force if the separation between two point masses doubles?
答案
It becomes one-fourth as large. The force follows an inverse-square dependence on distance.
卡片 68
问题
How can an adjustable incline estimate a block's coefficient of static friction when no other applied force acts?
答案
Raise the incline slowly until the block just begins to slide. At that threshold, the simple block model gives μ_s = tan θ.
卡片 69
问题
In an inertial frame, what determines the acceleration of a fixed-mass system's center of mass?
答案
The net external force divided by the system's total mass. Internal force pairs cannot change the center-of-mass motion of the whole system.
卡片 70
问题
Which tension components act for a conical pendulum?
答案
The vertical component balances weight, and the horizontal component supplies centripetal force. The bob moves in a horizontal circle.
卡片 71
问题
What does apparent weight measure for an object supported by one surface?
答案
The normal-force magnitude exerted by that support. It can differ from gravitational force when the object accelerates.
卡片 72
问题
How are several forces combined to find net force?
答案
Add them as vectors, component by component. Opposing components subtract according to the chosen signs.
卡片 73
问题
Why is tension uniform along one continuous ideal string?
答案
Every massless segment must have zero net force in the ideal model. Without frictional contact or a massive pulley changing it, the tension magnitude stays the same throughout the string.
卡片 74
问题
A 0.5 kg object moves at 4 m/s in a circle of radius 2 m. What inward net force is required?
答案
4 N. F_in = mv²/r = 0.5 × 16 / 2.
卡片 75
问题
What local equivalence links a uniform gravitational field with a uniformly accelerating reference frame?
答案
A uniform gravitational field and a uniformly accelerating reference frame can produce the same local mechanical effects. Local observations alone may not distinguish them.
卡片 76
问题
For the same net force, what happens to acceleration if mass doubles?
答案
Acceleration is halved. From a = ΣF/m, acceleration is inversely proportional to mass.
卡片 77
问题
How do static and kinetic friction coefficients usually compare for the same pair of surfaces?
答案
Typically μ_s > μ_k. Starting sliding usually requires a larger friction threshold than maintaining it.
卡片 78
问题
How are radial and tangential acceleration combined when circular speed changes?
答案
Add the perpendicular components as vectors. The total magnitude is √(a_c² + a_t²).
卡片 79
问题
A spherically symmetric planet has twice Earth's mass and the same radius. How does its surface g compare with Earth's?
答案
It is twice as large. Surface field strength follows g = GM/R².
卡片 80
问题
Does a force have to point in the direction of motion?
答案
No. A force points in the direction of the interaction; it may speed up, slow down, or turn the object.
卡片 81
问题
Where is the center of mass of a uniform object with a symmetric mass distribution?
答案
At its geometric center of symmetry. Symmetry lets opposite mass elements balance without a detailed sum.
卡片 82
问题
How are speed, period, and frequency related in uniform circular motion?
答案
v = 2πr/T = 2πrf, with T = 1/f. One cycle covers one circumference.
卡片 83
问题
Why is an object apparently weightless in free fall?
答案
Its support force is zero while it and its surroundings accelerate together under gravity. Gravity still acts.
卡片 84
问题
Can forces balance along one axis while an object accelerates along another?
答案
Yes. Zero net force in one component gives zero acceleration only in that direction; another component can remain unbalanced.
卡片 85
问题
Why don't Newton's third-law forces cancel on one object's free-body diagram?
答案
Only one force in the pair acts on that object. The partner force belongs on the other object's diagram.
卡片 86
问题
On a frictionless banked curve, which force components create vertical balance and inward acceleration?
答案
The normal force's vertical component balances weight, while its horizontal component supplies the inward net force.
卡片 87
问题
What motion results when the net force on an object is zero in an inertial frame?
答案
Constant velocity. Rest is the special case with constant velocity equal to zero.
卡片 88
问题
A 3 kg cart has a net horizontal force of 12 N. What is its acceleration?
答案
4 m/s². Use a = ΣF/m = 12/3.
卡片 89
问题
What does the observed equivalence of inertial and gravitational mass imply for free fall?
答案
Free-fall acceleration is independent of the falling object's mass. Inertial and gravitational mass are proportional and conventionally assigned equal numerical values.
卡片 90
问题
Does friction in the simple dry-friction model depend on apparent contact area?
答案
No. For a fixed normal force and the same contacting materials, the model treats friction magnitude as independent of apparent contact area.
卡片 91
问题
When should Hooke's-law predictions be treated cautiously?
答案
When deformation leaves the spring's linear elastic range. Force may no longer be proportional to displacement.
卡片 92
问题
What bank angle θ supports speed v on an ideal frictionless curve of radius r?
答案
tan θ = v²/(rg). The result assumes no vertical acceleration and no friction.
卡片 93
问题
Why do internal forces cancel when finding the net force on a complete system?
答案
They occur in equal-and-opposite pairs between system parts. Each pair sums to zero in the system's force total.
卡片 94
问题
An elevator moves downward at constant speed. How does the scale reading compare with weight?
答案
It equals the weight. Constant velocity means zero acceleration and N - mg = 0.
卡片 95
问题
What assumptions let an ideal pulley redirect a string without changing its tension magnitude?
答案
The pulley is massless and frictionless, and the string is ideal. It changes the tension's direction while the magnitude stays the same on both sides.
卡片 96
问题
What does inertia describe?
答案
An object's resistance to changes in velocity. Mass measures translational inertia.
卡片 97
问题
For the same fixed-mass object or system across all measurements, what does the slope of a net-force-versus-acceleration graph represent?
答案
Its mass. Written as ΣF = ma, the graph has slope m when the object or system and its mass stay fixed.
卡片 98
问题
Does zero net force mean no forces act?
答案
No. Several forces can act and cancel vectorially.
卡片 99
问题
What is the common model for kinetic-friction magnitude?
答案
f_k = μ_kN. It applies while the surfaces slide under the model's assumptions.
卡片 100
问题
How could hanging masses measure the spring constant of one ideal spring?
答案
At static equilibrium, record the spring's extension for several known weights and graph mg versus extension. Keep the same spring in its linear range; the slope is k.
卡片 101
问题
For the same object at the same circular radius, how does required inward net force change if speed doubles?
答案
It becomes four times as large. F_in = mv²/r depends on speed squared.
卡片 102
问题
Where is the center of mass of two point masses on an x-axis?
答案
At x_cm = (m₁x₁ + m₂x₂)/(m₁ + m₂). It lies closer to the larger mass.
卡片 103
问题
Why must net force, rather than one selected force, be used in ΣF = ma?
答案
All external forces contribute to acceleration. Ignoring a force changes the vector sum and the prediction.
卡片 104
问题
Why can tension vary along a hanging chain with nonnegligible mass?
答案
Higher sections must support and accelerate more chain below them. Newton's third law still applies locally to each interaction; it does not make tension uniform everywhere.
卡片 105
问题
What makes a reference frame inertial?
答案
An object with zero net force has constant velocity in that frame. A frame accelerating relative to an inertial frame is noninertial.
卡片 106
问题
How could carts test the proportionality between acceleration and net force?
答案
Keep total mass constant, vary the applied net force, and graph acceleration versus force. A line through the origin supports a ∝ ΣF.
卡片 107
问题
How does Kepler's third-law scaling compare two satellites in circular orbits at center-to-center radii r when their masses are negligible relative to the same fixed central mass?
答案
T² ∝ r³. The circular orbit with the larger center-to-center radius has the longer period.
卡片 108
问题
Which direction does kinetic friction act?
答案
Opposite the relative sliding of the contacting surfaces. It is not automatically opposite the object's velocity in every frame.
卡片 109
问题
What does the slope of a spring-force-versus-displacement graph give?
答案
-k when signed force is graphed against signed displacement. The slope magnitude is the spring constant.
卡片 110
问题
What is the minimum speed at the top of an ideal vertical loop of radius r when gravity alone supplies the inward force?
答案
v_min = √(gr). At the threshold, the support force or tension is zero.
卡片 111
问题
What is translational kinetic energy?
答案
Energy associated with an object's translational motion. For a point-like object, K = ½mv².
卡片 112
问题
How is work by a constant force calculated when its point of application undergoes a straight displacement?
答案
W = Fd cos θ. Here d is the displacement of the force's point of application, and θ is the angle between the force and that displacement.
卡片 113
问题
What does power measure?
答案
The rate of energy transfer or conversion. P_avg = ΔE_transferred/Δt; when work is the relevant transfer, P_avg = W/Δt.
卡片 114
问题
What does conservation of energy say for an isolated system?
答案
The system's total energy stays constant. Energy may change form or move among system parts, but it is not created or destroyed.
卡片 115
问题
Can translational kinetic energy be negative?
答案
No. Mass is positive and speed is squared, so translational kinetic energy is zero or positive.
卡片 116
问题
What does negative work by a force mean?
答案
The force makes a negative contribution to the system's kinetic-energy change. Its component opposes the displacement of its point of application; potential energy may rise while total mechanical energy stays constant.
卡片 117
问题
What is the near-surface change in gravitational potential energy?
答案
ΔU_g = mgΔy. It applies when g can be treated as constant.
卡片 118
问题
When is a chosen system's mechanical energy K + U conserved?
答案
When no net energy crosses the system boundary and no internal process converts energy in either direction between mechanical and nonmechanical forms. If either condition fails, K + U can change even though total energy still balances for the system plus surroundings.
卡片 119
问题
What is the SI unit of power?
答案
The watt, W. One watt equals one joule per second.
卡片 120
问题
For an object modeled as a particle, what connects net work by all forces to its change in translational kinetic energy?
答案
The work–energy theorem: W_net = ΔK. Under the particle model, positive net work raises translational kinetic energy and negative net work lowers it. A rotating rigid system requires total kinetic energy and work at the forces' points of application.
卡片 121
问题
A ball falls from rest through height h near a planet's surface. For the ball–planet system, g is constant and air resistance is negligible. What speed does energy conservation predict?
答案
v = √(2gh). The system's mgh decrease in gravitational potential energy becomes ½mv².
卡片 122
问题
Does choosing a different zero level for potential energy change physical predictions?
答案
No. Only potential-energy differences enter measurable energy changes.
卡片 123
问题
Can an engine do the same work with different average power?
答案
Yes. Doing the same work in less time requires greater average power.
卡片 124
问题
When does a constant nonzero force do zero work over an interval?
答案
When its point of application has zero displacement or its displacement is perpendicular to the force. Then W = Fd cos θ is zero.
卡片 125
问题
A particle-modeled block slides down a fixed frictionless track. Does the path shape affect its final speed at a given lower height?
答案
No. With only gravity doing work, the potential-energy change depends on height, not path.
卡片 126
问题
How does translational kinetic energy change if speed doubles at constant mass?
答案
It becomes four times as large. Kinetic energy depends on v².
卡片 127
问题
What is the elastic potential energy of an ideal spring displaced by a signed amount x from its relaxed or natural length, with U_s = 0 there?
答案
U_s = ½kx². Choosing zero energy at the relaxed length gives the same stored energy for equal-magnitude extension or compression.
卡片 128
问题
What does signed area under a force-component-versus-position graph represent when position tracks that force's point of application?
答案
Work done by that force along the measured coordinate. Area below the position axis counts as negative work under the graph's sign convention.
卡片 129
问题
A chosen system starts with 20 J of mechanical energy and converts 6 J of it into thermal energy, with no energy crossing the boundary. How much mechanical energy remains?
答案
14 J. The 6 J thermal-energy increase matches the mechanical-energy decrease.
卡片 130
问题
What shape does a translational-kinetic-energy-versus-speed graph have for fixed mass?
答案
The right-hand half of an upward-opening parabola through the origin. Speed is nonnegative, and K is proportional to v², not v.
卡片 131
问题
A machine transfers 600 J in 3 s. What is its average power?
答案
200 W. Divide energy transferred by elapsed time.
卡片 132
问题
Why does the normal force do no work on a nonrotating block sliding across a fixed horizontal floor?
答案
The force is perpendicular to the horizontal displacement of its points of application. Their dot product is zero in this pure-translation model.
卡片 133
问题
A coaster modeled as a particle moves on a fixed frictionless track. Where is its speed greatest?
答案
At the lowest accessible position. Gravitational potential energy is smallest there, so kinetic energy is largest.
卡片 134
问题
Two objects have equal mass and velocities of equal magnitude but opposite direction. How do their translational kinetic energies compare?
答案
They are equal. Kinetic energy uses speed and has no direction.
卡片 135
问题
What makes work by a conservative force path independent?
答案
It depends only on the initial and final configurations. Any two paths between the same endpoints give the same conservative-force work.
卡片 136
问题
A 10 N force acts while its point of application moves 3 m in the force direction. How much work does the force do?
答案
30 J. Here θ = 0, so W = Fd = 10×3.
卡片 137
问题
How is total potential energy built for a system with several interacting pairs?
答案
Add the potential energy assigned to each relevant pair. Count each interaction pair once and use one consistent reference choice.
卡片 138
问题
How should external work appear in an energy equation?
答案
As energy transferred across the system boundary. A useful form is ΔE_system = W_external + other transfers.
卡片 139
问题
How does a spring launch problem combine energy forms?
答案
Initial elastic energy becomes kinetic energy and possibly gravitational or thermal energy. Write only the forms present in the chosen initial and final states.
卡片 140
问题
For a constant force parallel to the velocity of its point of application, how is instantaneous mechanical power calculated?
答案
P = Fv. More generally, P = F·v_point, so only the force component along that point's velocity contributes.
卡片 141
问题
How does translational kinetic energy change if mass triples at constant speed?
答案
It triples. Kinetic energy is directly proportional to mass.
卡片 142
问题
How much net work does a conservative force do around a path that returns to the initial configuration?
答案
Zero. The initial and final potential energies are the same.
卡片 143
问题
Where is stable equilibrium on a potential-energy-versus-position graph?
答案
At a local minimum. Small displacements produce forces that point back toward the minimum.
卡片 144
问题
Which displacement belongs in the work done by a force on a rigid object?
答案
The displacement of that force's point of application. Using the center-of-mass displacement can be wrong when the object also rotates.
卡片 145
问题
What happens to mechanical energy when kinetic friction acts inside the chosen system?
答案
Some mechanical energy becomes thermal energy. The broader system's total energy still balances.
卡片 146
问题
A nonrotating particle falls from rest through vertical drop h under constant g. If its gravitational-potential decrease becomes only translational kinetic energy, with no other energy changes, what graph linearizes final speed?
答案
Graph v² versus drop height h. Under those conditions, v² = 2gh, so the slope should be 2g.
卡片 147
问题
If two students start and finish a stair climb at the same speeds, how could data compare their average mechanical output power against gravity?
答案
Measure each student's mass, vertical rise, and climb time, then calculate mgh/t. Equal initial and final speeds make ΔK = 0; if ΔK is negligible, the result is an approximation. This is mechanical output power against gravity, not metabolic input power.
卡片 148
问题
How can force-sensor data measure work when force changes as its point of application moves?
答案
Graph the force component along the motion against the point-of-application position and find the signed area. A rectangle formula isn't enough for a varying force.
卡片 149
问题
Why is potential energy assigned to a system rather than one isolated object?
答案
It belongs to an interaction between system parts. Gravitational potential energy, for example, belongs to the object–Earth system.
卡片 150
问题
How can work by a nonconservative force depend on path?
答案
Different routes can have different force histories or path lengths. Kinetic-friction work, for example, can change with distance traveled.
卡片 151
问题
A 2 kg cart moves at 3 m/s. What is its translational kinetic energy?
答案
9 J. K = ½(2)(3²) = 9 J.
卡片 152
问题
A block slides distance d across a stationary surface while constant kinetic friction f_k opposes its displacement. What work does friction do on the block?
答案
W_f = -f_k d. The negative sign follows from friction pointing opposite the block's displacement in this stated setup.
卡片 153
问题
A 2 kg object rises 5 m where g = 10 m/s². What is ΔU_g?
答案
+100 J. ΔU_g = mgΔy = 2 × 10 × 5.
卡片 154
问题
Why are energy bar charts useful?
答案
They make initial energy, final energy, and transfers explicit. A correct chart respects the chosen system and reference levels.
卡片 155
问题
A motor lifts the same load through the same height twice as fast. Both lifts begin and end at the same speeds and have equal or negligible dissipative losses. How do the motor's mechanical output work and average power compare?
答案
The mechanical output work is unchanged, while average power doubles. The two lifts have the same ΔU_g, the same ΔK, and the same losses, so the same output energy is delivered in half the time.
卡片 156
问题
A nonrotating 1 kg block starts from rest and receives 18 J of net work. What speed does it reach?
答案
6 m/s. For this pure-translation model, ΔK = 18 J = ½(1)v².
卡片 157
问题
Why is gravitational potential energy lower when two attracting point masses—or nonoverlapping spherical bodies—are closer in the inverse-square model?
答案
Energy must be supplied to separate them. With zero chosen at infinite center-to-center separation, U_g = -GMm/r.
卡片 158
问题
What does a steep potential-energy graph imply about force magnitude in one dimension?
答案
A large force magnitude. Force points toward decreasing potential energy and corresponds to the negative slope of U(x).
卡片 159
问题
An ideal spring with k = 80 N/m is compressed 0.50 m from its relaxed length. With U_s = 0 at that length, what elastic energy is stored?
答案
10 J. U_s = ½(80)(0.50²).
卡片 160
问题
A constant 50 N force acts while its point of application moves at 4 m/s in the force direction. What mechanical power is delivered?
答案
200 W. P = Fv_point = 50 × 4.
卡片 161
问题
If potential energy decreases by 30 J and no energy crosses the system boundary, what happens to the other energy forms?
答案
They increase by a total of 30 J. Often kinetic energy rises, but thermal or other forms may share the increase.
卡片 162
问题
Does an object's translational kinetic energy depend on the reference frame?
答案
Yes. Different inertial observers can measure different speeds and therefore different K = ½mv² for the same object.
卡片 163
问题
Why can work depend on the system boundary?
答案
Changing the system can reclassify energy transfer. For example, friction may be external work on one system but internal thermal-energy conversion in a larger system.
卡片 164
问题
A force-component-versus-position graph for the force's point of application forms a triangle of base 4 m and height 6 N above the axis. What work does it show?
答案
12 J. The signed area is ½×4×6.
卡片 165
问题
A motor transfers 50 J into a chosen system while another device transfers 12 J out. What is the net system-energy change?
答案
+38 J. Add the signed transfers across the boundary: 50 J - 12 J.
卡片 166
问题
What is the clearest first step in an energy-conservation problem?
答案
Choose the system and the initial and final states. That choice determines which energies and transfers belong in the equation.
卡片 167
问题
Why can energy methods solve some problems without finding time?
答案
Energy connects states through position, speed, and transfers. Time is absent unless power or a time-dependent process matters.
卡片 168
问题
Why can a force's instantaneous mechanical power be zero while the force is nonzero?
答案
Its point of application may be instantaneously at rest, or the force may be perpendicular to that point's velocity. In either case F·v_point = 0.
卡片 169
问题
What is the SI unit of kinetic energy?
答案
The joule, J. One joule equals 1 kg·m²/s².
卡片 170
问题
How is work by a conservative force related to potential-energy change?
答案
W_conservative = -ΔU. When the conservative force does positive work, potential energy falls.
卡片 171
问题
Where is unstable equilibrium on a potential-energy-versus-position graph?
答案
At a local maximum. A small displacement produces a force that pushes the system farther away.
卡片 172
问题
For a particle moving in a circle at constant speed, does the inward net force change its translational kinetic energy?
答案
No. The inward net force is perpendicular to the particle's instantaneous velocity, so its net work is zero and it changes the velocity's direction rather than its magnitude.
卡片 173
问题
Why should thermal energy not be written as a force?
答案
Thermal energy is an energy store, not an interaction force. Friction is the interaction that converts or transfers energy.
卡片 174
问题
How could a ramp experiment test mechanical-energy conservation for a cart–Earth system when the cart is modeled as a particle?
答案
Measure speed and height at several points, calculate K + U_g with one consistent zero level, and compare within uncertainty. Systematic drift suggests unmodeled energy transfer or conversion.
卡片 175
问题
According to the plotted power's definition and sign convention, what does signed area under a power-versus-time graph represent?
答案
Energy transferred or converted over the interval. Interpret positive and negative areas using the graph's stated sign convention and what its power represents.
卡片 176
问题
What is linear momentum?
答案
p = mv. Momentum is a vector in the direction of velocity and uses SI units kg·m/s.
卡片 177
问题
How is a multi-object system's total momentum found?
答案
Add every object's momentum as a vector. In one dimension, add signed values.
卡片 178
问题
For a chosen object or system, what is external impulse?
答案
The change in its momentum: J_external = Δp. For constant net external force, J_external = F_net,external Δt.
卡片 179
问题
What experimental uncertainty matters strongly when comparing collision kinetic energies?
答案
Velocity uncertainty. Because K depends on v², small speed errors can produce larger relative energy errors.
卡片 180
问题
Why can two objects bounce apart yet still collide inelastically?
答案
Bouncing does not guarantee kinetic-energy conservation. Some kinetic energy becomes internal or thermal energy through deformation, and some may be carried by sound.
卡片 181
问题
A 3 kg cart moves right at 4 m/s. What is its momentum if right is positive?
答案
+12 kg·m/s. p = mv = 3 × 4.
卡片 182
问题
Why can momentum be negative while kinetic energy cannot?
答案
Momentum carries direction through velocity's sign. Kinetic energy depends on speed squared.
卡片 183
问题
When is a system's total linear momentum conserved?
答案
When the net external impulse is zero or negligible during the interval. Internal impulses cancel in the system total.
卡片 184
问题
Two equal masses collide elastically in one dimension; one is initially at rest. What commonly happens?
答案
They exchange velocities. The incoming mass stops and the other leaves with its speed under the ideal conditions.
卡片 185
问题
Can total kinetic energy increase in an explosion?
答案
Yes. Stored internal energy can become kinetic energy. Total momentum is conserved for a defined system with zero or negligible net external impulse, while total energy remains conserved for the system plus surroundings.
卡片 186
问题
How is total momentum related to center-of-mass velocity?
答案
p_total = Mv_cm. M is the system's total mass.
卡片 187
问题
How does a nonzero external impulse affect system momentum?
答案
It changes total momentum by that impulse. J_external = Δp_system.
卡片 188
问题
Two carts start at rest and push apart with negligible external horizontal impulse. How do their final momenta compare?
答案
They are equal in magnitude and opposite in direction. The system began with zero total momentum.
卡片 189
问题
What are equivalent SI units for impulse?
答案
N·s and kg·m/s. Both represent a change in momentum.
卡片 190
问题
What defines an elastic collision?
答案
Both total momentum and total kinetic energy are conserved for the chosen isolated system. Individual objects may exchange both quantities.
卡片 191
问题
How can a force sensor and motion detector test the impulse–momentum theorem for one cart?
答案
Account for every external force component along the measured axis, compare the net-force–time area with m(v_f - v_i), and include uncertainty. Agreement supports J_external = Δp.
卡片 192
问题
A person jumps right from a stationary boat. Neglecting external horizontal impulse, which way does the boat move?
答案
Left. The person and boat acquire opposite momenta so total momentum remains zero.
卡片 193
问题
Why must momentum signs be kept through an impulse calculation?
答案
Impulse changes a vector quantity. Reversal can make Δp larger than either momentum magnitude alone.
卡片 194
问题
What defines a perfectly inelastic collision?
答案
The objects stick together after impact. Momentum is conserved in an isolated system, but kinetic energy decreases as much as the constraints allow.
卡片 195
问题
Why can momentum be conserved during a collision even when large forces act?
答案
For a defined system with zero or negligible net external impulse, the large collision forces are internal. Their equal-and-opposite impulses cancel within that system.
卡片 196
问题
Two objects have equal speed. Which has the larger momentum magnitude?
答案
The object with larger mass. At equal speed, momentum is proportional to mass.
卡片 197
问题
How is momentum conservation written for a two-dimensional isolated interaction?
答案
Conserve components separately: Σp_x,i = Σp_x,f and Σp_y,i = Σp_y,f. Both component equations must hold for the same interaction.
卡片 198
问题
For a chosen object or system, how is average net external force related to impulse?
答案
F_avg,external = Δp/Δt. For the same momentum change, a longer interaction time gives a smaller average force.
卡片 199
问题
Which conservation law alone can determine the shared final velocity of a sticking collision?
答案
Linear momentum conservation, if external impulse is negligible. Kinetic energy is not conserved in the sticking process.
卡片 200
问题
Two equal momentum vectors point along +x and +y. What direction does their total momentum point?
答案
At 45° between the positive axes. Equal perpendicular components produce that resultant direction.
400张卡片
Algebra-Based Physics 1 Flashcards: Complete 8-Unit Course Review
免费学习这套卡组
Flashcards 将打开，你可以立即开始学习。
卡片 201
问题
If external impulse during a collision is small but not zero, what should experimental data show?
答案
Final total momentum should be close to, but not exactly equal to, initial total momentum. The difference estimates external impulse.
卡片 202
问题
A force–time pulse has the same area but twice the peak force and half the duration. How does its impulse change?
答案
It does not change. Impulse depends on total signed area, not peak force alone.
卡片 203
问题
A 1 kg cart at 4 m/s sticks to an identical stationary cart. If external impulse is negligible, how does final kinetic energy compare with the initial 8 J?
答案
It is 4 J, half the initial value. The 4 J decrease in translational kinetic energy becomes internal or thermal energy through deformation, and some energy may be carried by sound.
卡片 204
问题
How can a nearly frictionless cart track improve a momentum-conservation test?
答案
It reduces external horizontal impulse during the collision. That makes the two-cart system closer to isolated.
卡片 205
问题
How does an object's momentum change if its speed doubles at constant mass?
答案
Its momentum magnitude doubles. Momentum depends linearly on speed.
卡片 206
问题
For a chosen object or system, what does signed area under its net-external-force-versus-time graph represent?
答案
External impulse, which equals the change in that object's or system's momentum. Area below the time axis contributes negative impulse under the graph's sign convention.
卡片 207
问题
A firework at rest explodes into two pieces with negligible external impulse. If one piece has twice the mass, how do the piece speeds compare?
答案
The heavier piece moves at half the speed of the lighter piece. Their momentum magnitudes must match.
卡片 208
问题
Why is sticking evidence of an inelastic collision?
答案
The objects share one final velocity, while some translational kinetic energy becomes internal or thermal energy through deformation. Translational kinetic energy is not conserved.
卡片 209
问题
Can a moving two-object system have zero total momentum?
答案
Yes. Equal and opposite momenta cancel even though each object is moving.
卡片 210
问题
A constant 6 N net external force acts on a chosen object for 0.5 s. What impulse does it deliver?
答案
3 N·s in the force direction. Multiply the net external force by the interaction time.
卡片 211
问题
What does a momentum-versus-velocity graph's slope represent for one object?
答案
Its mass. The relationship p = mv is linear through the origin.
卡片 212
问题
A 2 kg cart at +3 m/s sticks to a 1 kg cart at rest. If external horizontal impulse is negligible, what is their final velocity?
答案
+2 m/s. Momentum conservation gives (2×3 + 1×0)/(2+1).
卡片 213
问题
An isolated two-dimensional interaction has known initial total momentum p_total,i and known first outgoing momentum p₁,f. How is the second outgoing momentum found?
答案
Subtract component by component: p₂,f = p_total,i - p₁,f. Thus p₂x,f = p_total,x,i - p₁x,f, with the same subtraction for y.
卡片 214
问题
A 2 kg ball changes velocity from +3 m/s to -1 m/s. What impulse acts on it?
答案
-8 N·s. Δp = m(v_f - v_i) = 2(-1 - 3).
卡片 215
问题
What remains conserved in an isolated inelastic collision?
答案
Total momentum. Some kinetic energy becomes internal or thermal energy through deformation, and some may be carried by sound.
卡片 216
问题
Why does choosing both colliding objects as the system simplify momentum analysis?
答案
Their contact forces become internal. Only external impulse can change the system total.
卡片 217
问题
For a chosen object or system, what does the slope of its momentum-versus-time graph represent?
答案
Net external force. A steeper slope means a larger force in the slope's signed direction.
卡片 218
问题
Why do airbags reduce injury force during a stop?
答案
They increase the stopping time for roughly the same momentum change. That lowers the average force.
卡片 219
问题
A 1 kg cart at 4 m/s sticks to an identical stationary cart. If external impulse is negligible, what final speed do they share?
答案
2 m/s. Momentum 4 kg·m/s is shared by 2 kg.
卡片 220
问题
For a defined collision system with zero or negligible net external impulse, how can before-and-after velocity measurements classify the collision?
答案
First verify total momentum within uncertainty, then compare total kinetic energy. Unchanged kinetic energy supports elastic behavior; any change beyond uncertainty means the collision isn't elastic, with a decrease indicating an ordinary inelastic collision.
卡片 221
问题
What is angular displacement?
答案
The signed angle through which a rigid body rotates. In calculations, radians make the linear–angular relationships direct.
卡片 222
问题
For a rigid body rotating about a chosen fixed axis, what does angular velocity measure?
答案
Signed angular displacement per time about that axis. Average angular velocity is ω_avg = Δθ/Δt under one sign convention.
卡片 223
问题
For a rigid body rotating about a chosen fixed axis, what does angular acceleration measure?
答案
Change in signed angular velocity per time about that axis. Average angular acceleration is α_avg = Δω/Δt.
卡片 224
问题
What does rotational inertia measure?
答案
Resistance to angular acceleration about a specified axis. It depends on mass and how that mass is distributed relative to the axis.
卡片 225
问题
What is the lever arm in a torque calculation?
答案
The perpendicular distance from the axis to the force's line of action. It is not always the full distance to the contact point.
卡片 226
问题
For a planar rigid object in an inertial frame, what two conditions give simultaneous translational and rotational equilibrium?
答案
ΣF_external = 0 and Στ_external = 0 about a fixed axis. Static equilibrium also requires the object to be at rest.
卡片 227
问题
Two points lie on the same rotating rigid disk. Which rotational quantities are the same?
答案
They share angular displacement, angular velocity, and angular acceleration. Their linear speeds and accelerations can differ with radius.
卡片 228
问题
How is rotational inertia found for a collection of point masses?
答案
I_total = Σmᵢrᵢ². Each rᵢ is that mass's perpendicular distance from the chosen axis.
卡片 229
问题
What determines the magnitude of torque from one force about a chosen axis?
答案
τ = rF sin θ = r_perp F. The radius vector r runs from the axis to the force's point of application, θ is the angle between r and the force, and r_perp is the lever arm.
卡片 230
问题
What is Newton's second law for a rigid system rotating about an axis fixed in an inertial frame?
答案
Στ_external = Iα when rotational inertia I about that axis is constant. Net external torque and angular acceleration use the same signed-axis convention.
卡片 231
问题
For a point on a rigid body rotating about a fixed axis, how is signed arc displacement related to signed angular displacement in radians?
答案
Δs = rΔθ. Here r is the point's perpendicular distance from the fixed axis, and both displacements use matching sign conventions along the circular path.
卡片 232
问题
In a planar rigid-body model, can an object with zero net external force and zero net external torque about its center of mass be moving?
答案
Yes. Its center of mass may translate at constant velocity while it rotates at constant angular velocity; the stated zero net force and center-of-mass torque don't require rest.
卡片 233
问题
At an instant when ω ≠ 0, what do the signs of angular velocity and angular acceleration show about rotational speed?
答案
Matching signs mean the rotation speeds up; opposite signs mean it slows down. The sign convention chooses which rotation direction is positive.
卡片 234
问题
How are clockwise and counterclockwise torques combined?
答案
Choose one direction as positive and add signed torques. Net torque is the algebraic sum about the same axis.
卡片 235
问题
For the same rigid system with constant rotational inertia about the same axis fixed in an inertial frame, what happens if net-external-torque magnitude doubles?
答案
Angular-acceleration magnitude doubles. Under those conditions, |α| is directly proportional to |Στ_external|.
卡片 236
问题
Why must an axis be named when stating rotational inertia?
答案
The same object has different rotational inertia about different axes. Mass distribution relative to the chosen axis changes.
卡片 237
问题
For one rigid body rotating about a fixed axis, what does the slope of its angular-position-versus-time graph represent?
答案
Signed angular velocity about that axis. A constant slope means constant angular velocity under the graph's sign convention.
卡片 238
问题
Why is torque's unit N·m not called a joule?
答案
Torque and energy are different physical quantities despite matching unit dimensions. Torque describes rotational effectiveness of a force.
卡片 239
问题
A rigid wheel has constant I = 2 kg·m² about an axis fixed in an inertial frame and net external torque 8 N·m about that axis. What is its angular-acceleration magnitude?
答案
4 rad/s². |α| = |Στ_external|/I = 8/2.
卡片 240
问题
Where can the weight of a rigid object be treated as acting in a uniform gravitational field?
答案
At the object's center of mass. That single force gives the same net gravitational force and torque.
卡片 241
问题
For a point on a rigid body rotating about a fixed axis, how is tangential-speed magnitude related to angular velocity?
答案
v_t = r|ω|. Here r is the perpendicular distance from the fixed axis. Points farther from the axis move faster even though the rigid body has one angular velocity.
卡片 242
问题
For constant angular acceleration about one fixed axis, what does ω = ω₀ + αt retrieve?
答案
Angular velocity after elapsed time t. Use signed angular quantities about that axis over an interval with constant α.
卡片 243
问题
A free-body diagram for a rigid bar must support a torque calculation about a marked axis. What must it show besides each force's direction and magnitude?
答案
Each force's point of application or line of action relative to the axis. That geometry sets the lever arm and torque sign; omitting it can preserve the net-force picture while losing the net torque.
卡片 244
问题
For the same rigid system about the same axis fixed in an inertial frame, what does the slope of a net-external-torque-versus-angular-acceleration graph represent?
答案
Its constant rotational inertia I about that axis. The graph follows Στ_external = Iα.
卡片 245
问题
A thin hoop and solid disk have the same mass and radius and rotate about their central symmetry axes. With I_hoop = MR² and I_disk = ½MR², which has larger I?
答案
The hoop. More of its mass lies far from the axis.
卡片 246
问题
Why can a rigid object have zero net external force but nonzero net external torque?
答案
External forces can cancel as vectors while acting along different lines. The resulting couple can still change the object's rotation.
卡片 247
问题
Which constant-angular-acceleration equation connects angular velocity and angular displacement about one fixed axis without time?
答案
ω² = ω₀² + 2αΔθ. Use signed quantities about that axis over an interval with constant α.
卡片 248
问题
A 10 N perpendicular force acts 0.40 m from a pivot. What torque magnitude does it produce?
答案
4 N·m. τ = rF for a perpendicular force.
卡片 249
问题
For a rigid body rotating about a fixed axis, how is the signed tangential-acceleration component related to angular acceleration?
答案
For a positive tangent consistent with the angular sign convention, a_t = rα. Its alignment or opposition with velocity determines whether speed increases or decreases.
卡片 250
问题
Why can two equal-mass rigid wheels have different angular-acceleration magnitudes under equal net-external-torque magnitudes about comparable axes fixed in an inertial frame?
答案
Their rotational inertias about those axes can differ because their mass distributions differ. Mass alone doesn't set rotational response.
卡片 251
问题
For one rigid body rotating about a fixed axis, what does signed area under its angular-velocity-versus-time graph represent?
答案
Signed angular displacement about that axis. Area below the time axis contributes negative angular displacement under the graph's sign convention.
卡片 252
问题
A rigid object rests on a support that is slowly tilted in uniform gravity. If gravity and support contact are its only external interactions, sufficient static friction prevents slipping, and the motion is quasistatic, what marks the onset of tipping?
答案
The object's center-of-mass vertical line reaches the edge of its support region. Beyond that point, gravity produces an unbalanced tipping torque.
卡片 253
问题
A point is twice as far from a rigid wheel's fixed axis as another point. How do their tangential speeds compare?
答案
The farther point moves twice as fast. v_t is proportional to radius for their common angular-speed magnitude |ω|.
卡片 254
问题
Does moving the chosen pivot change an individual force's torque?
答案
Yes. Torque depends on the axis, though a correctly solved physical prediction stays consistent.
卡片 255
问题
How does the parallel-axis theorem relate rotational inertia to a parallel axis a distance d from the center of mass?
答案
I = I_cm + Md². Shifting the axis away from the center of mass increases rotational inertia.
卡片 256
问题
How could an experiment determine a rigid wheel's constant rotational inertia about an axis fixed in an inertial frame?
答案
Apply several known signed net external torques about that axis, measure signed angular acceleration, and graph torque versus α. The slope is I.
卡片 257
问题
For a point at perpendicular distance r > 0 from a rigid body's fixed rotation axis, what is the radial-acceleration magnitude?
答案
a_r = v_t²/r = rω². The acceleration points toward the axis. At r = 0, use a_r = rω² = 0; the quotient form isn't defined there.
卡片 258
问题
How could a meterstick experiment test torque balance?
答案
Hang known forces at measured lever arms and compare signed r_perp F values at equilibrium. Repeat with different pivot choices.
卡片 259
问题
For uniform rotation at frequency f, what is the angular-speed magnitude?
答案
|ω| = 2πf. One revolution is 2π rad, and uniform rotation has the same angular-speed magnitude throughout the cycle.
卡片 260
问题
Why is choosing the pivot at an unknown support force often useful?
答案
That force then has zero lever arm and drops out of the torque equation. The physical equilibrium does not depend on the calculation shortcut.
卡片 261
问题
Among parallel axes through or near a rigid object, which gives the minimum rotational inertia?
答案
The parallel axis through the center of mass. Any offset adds the positive term Md².
卡片 262
问题
Compare rigid systems with constant rotational inertia about comparable axes fixed in an inertial frame. If net external torque is the same but I triples, what happens to angular acceleration?
答案
It becomes one-third as large. For each stated system, α = Στ_external/I.
卡片 263
问题
A rigid wheel of radius 0.50 m has angular-speed magnitude 6 rad/s about its fixed axis. What is the rim speed?
答案
3 m/s. v_t = r|ω| = 0.50 × 6.
卡片 264
问题
A 30 N child sits 2 m left of a seesaw pivot. If the seesaw's own weight acts through the pivot, where should a 20 N child sit on the right for balance?
答案
3 m from the pivot. Balance torque magnitudes: 30×2 = 20×r.
卡片 265
问题
For constant angular acceleration about one fixed axis, what does Δθ = ω₀t + ½αt² retrieve?
答案
Angular displacement over elapsed time t. Use signed angular quantities about that axis; the equation combines the initial angular-velocity contribution with the change caused by constant α.
卡片 266
问题
A 20 N force acts at 30° to a radius vector of magnitude 0.60 m from a chosen axis. What torque magnitude results?
答案
6 N·m. |τ| = rF sin θ = 0.60 × 20 × sin 30°.
卡片 267
问题
How does moving mass farther from a rotation axis affect rotational inertia?
答案
It increases rotational inertia strongly. For a point mass, I = mr².
卡片 268
问题
How can angular-acceleration data compare two rigid objects' constant rotational inertias about comparable axes fixed in an inertial frame?
答案
Apply the same measured net-external-torque magnitude about each axis and compare |α|. The object with smaller angular-acceleration magnitude has larger I.
卡片 269
问题
Why must angular displacement be in radians for Δs = rΔθ?
答案
Radians define angle as arc length divided by radius. Degree measure would require a conversion factor.
卡片 270
问题
When does a nonzero force produce zero torque about an axis?
答案
When its line of action passes through the axis. The lever arm is then zero.
卡片 271
问题
What is angular momentum for a rigid object rotating about an axis fixed in an inertial frame?
答案
L = Iω about that axis. Use one signed-axis convention consistently for L and ω.
卡片 272
问题
What magnitude relation holds for a planar, constant-radius rigid object whose center of mass lies on its rolling axis when it rolls without slipping on a stationary surface?
答案
v_cm = R|ω|. Here R is the constant rolling radius; the contact point is instantaneously at rest relative to the surface.
卡片 273
问题
For a rigid system rotating about an axis fixed in an inertial frame, how is work by a constant torque about that axis related to angular displacement?
答案
W = τΔθ when torque and angular displacement use the same signed axis. The angle must be in radians.
卡片 274
问题
For point masses—or nonoverlapping spherical bodies—M and m separated center to center by r, what is gravitational potential energy with zero at infinity?
答案
U_g = -GMm/r. The negative sign reflects U_g = 0 at infinity and attraction. In an isolated gravity-only inverse-square system, total mechanical energy determines binding: E < 0 is bound, while E ≥ 0 is unbound.
卡片 275
问题
When is a chosen system's angular momentum about an axis fixed in an inertial frame conserved?
答案
When net external torque on the system about that axis is zero or negligible over the interval. Internal torques cannot change the system total.
卡片 276
问题
What does kinetic friction do to mechanical energy while a wheel slips on a stationary surface?
答案
It converts mechanical energy into internal or thermal energy while the surfaces slide. Use qualitative energy accounting here; no no-slip relation connects the magnitudes v_cm and R|ω| during the slip.
卡片 277
问题
What is the angular-momentum magnitude of a translating point object about a chosen fixed point in an inertial frame?
答案
L = mvr sin θ = r_perp mv. Here r points from the chosen point to the object, v is its speed, and θ is the angle between them. The SI unit is kg·m²/s.
卡片 278
问题
For a satellite of negligible mass relative to a fixed central body, how do speed and energy change along one gravity-only elliptical orbit?
答案
Speed and kinetic energy are greatest near the central body, while gravitational potential energy is greatest farther away. Total mechanical energy stays constant.
卡片 279
问题
What is a rigid body's rotational kinetic energy about a fixed axis?
答案
K_rot = ½Iω². It depends on rotational inertia about that axis and angular speed.
卡片 280
问题
Two planar rigid objects with constant rolling radii and centers of mass on their rolling axes are released from rest on the same fixed incline. Each rolls without slipping under gravity and its contact forces, with no other applied force or torque and negligible dissipation. Which accelerates faster: the one with smaller or larger I_cm/(MR²)?
答案
The one with smaller I_cm/(MR²). Here I_cm is rotational inertia about the center of mass, M is total mass, and R is that object's constant rolling radius. Under the stated model, a_cm = g sin θ/(1 + I_cm/(MR²)).
卡片 281
问题
How could a rotating-platform experiment test angular-momentum conservation about the platform's axis, treated as fixed in the lab's inertial frame?
答案
Choose the platform, rider, and moved masses as one system. In both the initial and final arrangements, wait until the rider and moved masses are stationary relative to the platform and the whole system co-rotates with one common signed angular velocity; then measure I_i, ω_i, I_f, and ω_f and compare I_iω_i with I_fω_f. Keep net external torque about the axis negligible, reduce bearing friction, and include uncertainty.
卡片 282
问题
For a satellite of mass m negligible beside a fixed central mass M, how are K, U_g, and total mechanical energy E related in a gravity-only circular orbit at center-to-center radius r?
答案
K = -U_g/2 and E = U_g/2 = -K. Since U_g = -GMm/r, this gives K = GMm/(2r) and E = -GMm/(2r).
卡片 283
问题
For a rigid system rotating about an axis fixed in an inertial frame, how is instantaneous mechanical power delivered by a torque about that axis related to angular velocity?
答案
P = τω for signed torque and angular velocity about the same axis. It is the rotational counterpart of P = F·v_point.
卡片 284
问题
In a planar common-axis rigid-body model, what kinetic-energy expression applies to a body rolling without slipping, with I_cm and ω taken about the same axis through its center of mass?
答案
K = ½Mv_cm² + ½I_cmω². In this model, the rigid body's motion combines center-of-mass translation with rotation about one axis through the center of mass. I_cm and ω must refer to that same axis.
卡片 285
问题
Does angular-momentum conservation require rotational kinetic-energy conservation?
答案
No. Internal work can change rotational kinetic energy while angular momentum stays constant.
卡片 286
问题
Why do astronauts feel weightless in orbit even though gravity acts on them?
答案
They and their spacecraft are in continuous free fall together. Apparent weight is small because support forces are small.
卡片 287
问题
Two wheels spin at the same angular speed. Which has more rotational kinetic energy?
答案
The wheel with larger rotational inertia. At common ω, K_rot is proportional to I.
卡片 288
问题
For a chosen system, what does the slope of its angular-momentum-versus-time graph about an axis fixed in an inertial frame represent?
答案
Net external torque on the system about that axis. A constant slope means constant signed net external torque there.
卡片 289
问题
A motor supplies 12 N·m of torque about a shaft axis fixed in the lab's inertial frame while the shaft turns in the torque direction at 10 rad/s. What mechanical power does it deliver?
答案
120 W. Using signed quantities about the shaft axis, P = τω = 12×10.
卡片 290
问题
While a rigid wheel is slipping on a stationary surface, how are the magnitudes v_cm and R|ω| related?
答案
No no-slip equality applies. Their values evolve separately until friction may bring the contact point to rest relative to the surface.
卡片 291
问题
A launched object has negligible mass relative to a fixed central mass M and starts at center-to-center radius r. What minimum speed lets it escape under gravity alone without further propulsion or drag?
答案
v_escape = √(2GM/r). At that threshold, total mechanical energy is zero with the object reaching infinity at zero speed.
卡片 292
问题
In a planar common-axis rigid-body model, what kinetic-energy forms can a rigid body have when it translates and rotates about an axis through its center of mass?
答案
Both translational and rotational kinetic energy. The total is K = ½Mv_cm² + ½I_cmω², where I_cm and ω refer to the same axis through the center of mass.
卡片 293
问题
For a chosen object or system, what is angular impulse about an axis fixed in an inertial frame?
答案
The change in that object or system's angular momentum about the axis. For constant net external torque, ΔL = τ_net,external Δt. Use the same axis and sign convention throughout. Angular impulse has units N·m·s, equivalent to kg·m²/s.
卡片 294
问题
Two equal-mass planar rigid objects have constant rolling radii and centers of mass on their rolling axes. They start from rest at the same height and roll without slipping to the same lower endpoint with negligible dissipation. Why can their final speeds differ?
答案
Their rotational inertias divide the same decrease in gravitational potential energy differently between translation and rotation. A larger I_cm/(MR²) leaves less energy for translational speed, where I_cm is rotational inertia about the center of mass and R is rolling radius.
卡片 295
问题
For a satellite of negligible mass relative to a fixed central body, how does angular momentum behave along one gravity-only elliptical orbit?
答案
It stays constant because gravity exerts zero torque about the central body. The satellite moves faster when closer and slower when farther away.
卡片 296
问题
How does rotational kinetic energy change if angular speed doubles at fixed I?
答案
It becomes four times as large. Rotational kinetic energy depends on ω².
卡片 297
问题
Why should external torque be evaluated about the same axis used for angular momentum?
答案
Both quantities depend on the chosen axis. Mixing axes breaks the conservation statement.
卡片 298
问题
For a chosen object or system about an axis fixed in an inertial frame, what does signed area under its net-external-torque-versus-time graph represent?
答案
Angular impulse, equal to that object or system's ΔL about the axis. Use the graph's signed-axis convention. The area has units N·m·s, equivalent to kg·m²/s.
卡片 299
问题
Why can static friction act on a rigid object rolling without slipping on a stationary rigid surface without necessarily dissipating mechanical energy?
答案
The contact point is instantaneously at rest relative to the surface, so there is no sliding. Static friction can still supply the torque needed for rolling.
卡片 300
问题
For a satellite whose mass is negligible beside a fixed central mass M, what is its speed in a gravity-only circular orbit at center-to-center radius r?
答案
v = √(GM/r). Gravity supplies the inward net force.
卡片 301
问题
A chosen system's included mass co-rotates with one common angular velocity before and after a change. If its rotational inertia about an axis fixed in an inertial frame doubles while net external torque about that axis is negligible, what happens to its angular speed?
答案
It halves. Because all included mass shares one angular velocity in each state, L = Iω applies. With the same axis and sign convention, angular-momentum conservation gives I_iω_i = I_fω_f.
卡片 302
问题
For a rigid system rotating about an axis fixed in an inertial frame, what does signed area under its net-external-torque-versus-angular-position graph represent when angle is in radians?
答案
Net rotational work, equal to the system's change in rotational kinetic energy. Torque and angular position must use the same signed axis.
卡片 303
问题
Why can't the rolling condition alone prove that friction points uphill or downhill?
答案
Friction direction depends on the tendency to slip and the applied forces or torques. Solve the dynamics instead of guessing from motion.
卡片 304
问题
A satellite of mass m, negligible beside a fixed central mass M, follows a circular orbit at center-to-center radius r under gravity alone. What is its total mechanical energy?
答案
E = -GMm/(2r). A larger circular orbit has greater, less-negative energy even though its speed is lower.
卡片 305
问题
A spinning student pulls masses closer to an axis fixed in the lab's inertial frame while net external torque about that axis is negligible. Why does angular speed increase?
答案
Rotational inertia decreases while angular momentum stays constant. Therefore Iω remains constant by increasing ω.
卡片 306
问题
What makes simple harmonic motion a special kind of periodic motion?
答案
Its restoring force or torque is proportional to displacement and points toward equilibrium. Periodic motion alone does not guarantee this relationship.
卡片 307
问题
What does the amplitude of an SHM displacement graph represent?
答案
The maximum distance from equilibrium. It is nonnegative even though displacement alternates sign.
卡片 308
问题
How are period and frequency related?
答案
T = 1/f. Period is seconds per cycle; frequency is cycles per second, measured in hertz.
卡片 309
问题
What is the period of a mass m on an ideal spring of constant k when spring mass and damping are negligible?
答案
T = 2π√(m/k). The motion must stay in the spring's linear SHM range.
卡片 310
问题
For one-dimensional SHM, what is the equilibrium position?
答案
The position where the restoring force or torque—and therefore acceleration along the SHM coordinate—is zero. A stable equilibrium produces a restoring response after a small displacement.
卡片 311
问题
How far apart in phase are displacement and velocity in SHM?
答案
One-quarter cycle. Velocity reaches an extremum when displacement crosses zero.
卡片 312
问题
When can a simple pendulum be modeled as SHM?
答案
For small angular displacements. Then the restoring torque is approximately proportional to angular displacement.
卡片 313
问题
An oscillator completes 12 cycles in 6 s. What are its frequency and period?
答案
f = 2 Hz and T = 0.5 s. Frequency is cycles per time, and period is its reciprocal.
卡片 314
问题
For a horizontal ideal spring oscillator, what is potential energy at displacement x from its relaxed equilibrium length when U_s = 0 there?
答案
U_s = ½kx². It has the same value at +x and -x.
卡片 315
问题
At the equilibrium position of SHM, is the oscillator necessarily at rest?
答案
No. The restoring force or torque and acceleration along the SHM coordinate are zero there, but speed is usually greatest.
卡片 316
问题
How does a spring oscillator's period change if k becomes four times as large?
答案
The period is halved. T is proportional to 1/√k.
卡片 317
问题
How are acceleration and displacement related along the SHM coordinate?
答案
a = -ω²x, where ω = 2πf is the oscillation's angular frequency. Here ω describes the oscillator's phase rate, not a rigid body's rotational angular velocity. The acceleration component along the SHM coordinate points toward equilibrium.
卡片 318
问题
For a horizontal ideal spring oscillator with amplitude A, what is total mechanical energy when U_s = 0 at the relaxed equilibrium length?
答案
E = ½kA². It stays constant when dissipative effects are negligible.
卡片 319
问题
In a small-angle pendulum, where are speed and gravitational potential energy greatest?
答案
Speed is greatest at the bottom; gravitational potential energy is greatest at the turning points. Energy trades between those forms.
卡片 320
问题
How can frequency be read from an oscillation-versus-time graph?
答案
Measure the time between repeating equivalent points to find T, then use f = 1/T. Adjacent peaks are one period apart.
卡片 321
问题
Why does an ideal mass–spring oscillator exhibit SHM?
答案
Its net restoring force is F_net = -kx, where x is displacement from equilibrium. The force is proportional to displacement and points back toward equilibrium.
卡片 322
问题
A horizontal ideal spring has k = 50 N/m and amplitude 0.20 m. With U_s = 0 at equilibrium, what is the oscillator's total energy?
答案
1 J. E = ½(50)(0.20²).
卡片 323
问题
At maximum positive displacement in SHM, what are velocity and acceleration?
答案
Velocity is zero; acceleration has maximum magnitude toward equilibrium. With positive displacement, acceleration is negative.
卡片 324
问题
How does a spring oscillator's period change if its mass becomes four times as large?
答案
The period doubles. T is proportional to √m.
卡片 325
问题
Why isn't uniform circular motion itself one-dimensional SHM?
答案
The object travels around a circle, not back and forth along one line. Its projection onto a diameter does follow SHM.
卡片 326
问题
For the same ideal oscillator, how does total SHM energy change if amplitude doubles while k or mω² stays fixed?
答案
It becomes four times as large. Under those fixed system parameters, total energy is proportional to A².
卡片 327
问题
In one-dimensional SHM, what are speed and acceleration along the SHM coordinate at equilibrium?
答案
Speed is maximum, while acceleration along the SHM coordinate is zero. The restoring force or torque vanishes there.
卡片 328
问题
Does changing amplitude change the period of an ideal spring oscillator or small-angle pendulum?
答案
No within the ideal SHM model. The period depends on system parameters, not amplitude.
卡片 329
问题
How is maximum speed related to amplitude and angular frequency in SHM?
答案
v_max = ωA. Maximum speed occurs at equilibrium.
卡片 330
问题
For a horizontal ideal spring oscillator, how can kinetic energy at displacement x from equilibrium be found for amplitude A?
答案
K = ½k(A² - x²). Subtract spring potential energy from the constant total.
卡片 331
问题
How far apart in phase are displacement and acceleration in SHM?
答案
Half a cycle, or 180°. When displacement is nonzero, acceleration has the opposite sign; at equilibrium, both are zero.
卡片 332
问题
What is the period of a small-angle simple pendulum of length L when damping is negligible?
答案
T = 2π√(L/g). The simple-pendulum model uses a point-like bob on a light, inextensible string with a fixed support; bob mass doesn't affect the period.
卡片 333
问题
If x(t) is at a positive maximum at t = 0, what qualitative pattern follows over one cycle?
答案
It crosses equilibrium moving negative at T/4, reaches negative maximum at T/2, returns through equilibrium at 3T/4, and reaches maximum positive displacement at T.
卡片 334
问题
At equilibrium, how are a horizontal ideal spring oscillator's energies divided?
答案
Kinetic energy is maximum and spring potential energy is minimum. With x measured from equilibrium, U_s = 0 at x = 0.
卡片 335
问题
An SHM object is at negative displacement and moving toward equilibrium. What signs do velocity and acceleration have if positive is right?
答案
Both are positive. Motion and restoring acceleration point right toward equilibrium.
卡片 336
问题
How does a pendulum's period change if its length becomes nine times as large?
答案
The period triples. T is proportional to √L.
卡片 337
问题
If SHM starts at maximum positive displacement, what equation gives its position?
答案
x(t) = A cos(2πft). A is amplitude, f is frequency, and t is elapsed time.
卡片 338
问题
What feature would rule out ideal SHM in a force-versus-displacement-from-equilibrium graph?
答案
A restoring-force relationship that is not a straight line through the origin over the motion's range. Ideal SHM needs F ∝ -x.
卡片 339
问题
At a horizontal ideal spring oscillator's turning points, how are kinetic and spring potential energy divided?
答案
Kinetic energy is zero and spring potential energy is maximum. The object momentarily stops at |x| = A.
卡片 340
问题
For the same ideal spring with negligible damping and spring mass, which graph can determine k from measured periods and attached masses?
答案
Graph T² versus m. For T = 2π√(m/k), the slope is 4π²/k.
卡片 341
问题
What makes a substance a fluid?
答案
It deforms continuously under a shear force and takes the shape of its container. Liquids and gases are fluids.
卡片 342
问题
What is mass density?
答案
Mass per volume: ρ = m/V. Its SI unit is kg/m³.
卡片 343
问题
For pressure that is uniform over a surface patch, how is it related to normal force and area?
答案
P = F_perpendicular/A. Pressure is a scalar field even though the contact force has direction.
卡片 344
问题
What is volume flow rate?
答案
Volume passing a cross-section per time: Q = ΔV/Δt. Its SI unit is m³/s.
卡片 345
问题
What is the buoyant-force magnitude on an object immersed in a static fluid whose density is uniform over the displaced volume?
答案
The weight of the displaced fluid: F_B = ρ_fluid gV_displaced. Here ρ_fluid is the uniform density over that volume.
卡片 346
问题
What conditions support the basic Bernoulli model used here?
答案
Steady, incompressible, nonviscous flow along the compared flow path, with a completely filled pipe unless stated otherwise. Incompressible means a moving fluid element's density stays effectively constant. Pumps or major dissipative effects require extra terms.
卡片 347
问题
Under the ideal model, how does average density predict whether a free object floats or sinks?
答案
It floats if its average density is less than the fluid's and sinks if it is greater. Equal average density gives neutral buoyancy when fully submerged; assume no support or other external force.
卡片 348
问题
How are volume flow rate, cross-sectional area, and average fluid speed normal to that area related?
答案
Q = Av. This gives the volume crossing a completely filled pipe section per time.
卡片 349
问题
How does a static fluid exert force on a surface?
答案
Many particle–surface interactions produce a net force perpendicular to the surface. A static fluid does not exert a tangential shear force.
卡片 350
问题
How does pressure change with depth in a static uniform fluid?
答案
It increases by ΔP = ρgΔh. Greater depth means more fluid weight above each unit area.
卡片 351
问题
What force balance holds for an object floating at rest when buoyancy and weight are its only vertical forces?
答案
F_B = mg. The object's weight equals the weight of the fluid it displaces.
卡片 352
问题
What is the continuity equation for steady incompressible flow in one filled pipe?
答案
A₁v₁ = A₂v₂. The same volume flow rate passes each cross-section.
卡片 353
问题
Why does a static fluid produce an upward buoyant force?
答案
Pressure is greater on the object's lower surfaces than on its upper surfaces. The vertical pressure forces do not cancel.
卡片 354
问题
What is the absolute pressure at depth h below the open surface of a static, uniform liquid?
答案
P_abs = P_atm + ρgh. ρgh is the gauge pressure from the liquid column.
卡片 355
问题
Immediately after a fully submerged object is released in a static, uniform ideal fluid, which way does it accelerate if its average density exceeds the fluid density and only weight and buoyancy act?
答案
Downward. Weight exceeds buoyant force, so the initial net force and acceleration point downward.
卡片 356
问题
Water's average speed normal to a 0.020 m² pipe cross-section is 3 m/s. What is the volume flow rate?
答案
0.060 m³/s. Q = Av = 0.020×3.
卡片 357
问题
What does the slope of a mass-versus-volume graph represent for one uniform material?
答案
Density. Since m = ρV, the line's slope is ρ.
卡片 358
问题
How do gauge pressure and absolute pressure differ?
答案
Gauge pressure is measured relative to atmospheric pressure; absolute pressure is measured relative to vacuum. P_abs = P_atm + P_gauge.
卡片 359
问题
For a fully submerged rigid object in a static, incompressible, uniform fluid, does buoyant force increase with depth?
答案
No. Displaced volume, fluid density, and g stay constant, so F_B stays constant despite higher absolute pressure.
卡片 360
问题
For steady incompressible flow in a filled pipe, what happens to speed if cross-sectional area halves?
答案
It doubles. Continuity keeps Av constant.
卡片 361
问题
When does a fluid element's velocity change?
答案
Its velocity changes when a nonzero net force acts on it. Pressure forces and gravity can contribute to that net force.
卡片 362
问题
For steady, incompressible, nonviscous flow along the same flow path, what does Bernoulli's equation express?
答案
Conservation of mechanical energy per unit volume. Along that flow path, P + ½ρv² + ρgy stays constant under the stated conditions.
卡片 363
问题
For a uniform object floating at rest in a uniform-density fluid with buoyancy and weight as its only vertical forces, what fraction of its volume is submerged?
答案
V_sub/V_object = ρ_object/ρ_fluid. A less-dense object floats with a smaller fraction submerged.
卡片 364
问题
For steady incompressible flow in a filled pipe, what happens to speed if pipe radius halves?
答案
It becomes four times as large. Area is proportional to radius squared.
卡片 365
问题
What does Pascal's principle say for a confined incompressible fluid at rest?
答案
An applied pressure change is transmitted throughout the fluid. The same pressure change acts at every connected point.
卡片 366
问题
In a uniform static fluid, what does the slope of gauge pressure versus depth represent?
答案
ρg. For known g, the slope can determine fluid density.
卡片 367
问题
Immediately after a fully submerged object is released in a static, uniform ideal fluid, which way does it accelerate if its average density is less than the fluid density and only weight and buoyancy act?
答案
Upward. Buoyant force exceeds weight, so the initial net force and acceleration point upward.
卡片 368
问题
For steady incompressible flow in a filled pipe, area narrows from 0.040 m² to 0.010 m². If initial speed is 2 m/s, what is final speed?
答案
8 m/s. Continuity gives v₂ = A₁v₁/A₂.
卡片 369
问题
What physical quantity does each term in P + ½ρv² + ρgy share?
答案
Energy per unit volume, equivalent to pressure. Every term uses units of pascals.
卡片 370
问题
In one static fluid of uniform density, what experimental graph could test F_B = ρ_fluid gV_displaced?
答案
Graph measured buoyant force versus displaced volume. A line with slope near ρ_fluid g supports the model.
卡片 371
问题
A uniform object of density 750 kg/m³ floats at rest in uniform-density water of density 1000 kg/m³, with buoyancy and weight as its only vertical forces. What fraction is submerged?
答案
0.75, or 75%. Use the density ratio for floating equilibrium.
卡片 372
问题
A main pipe splits into two outlets during steady incompressible flow. What flow-rate relation holds?
答案
Incoming flow rate equals the sum of outgoing flow rates. Q_in = Q_out,1 + Q_out,2.
卡片 373
问题
For steady, incompressible, nonviscous efflux with negligible losses, what is Torricelli's speed for an opening a vertical distance h below a large open surface?
答案
v = √(2gh). Both locations are open to atmospheric pressure, and the large surface makes the upper-fluid speed negligible.
卡片 374
问题
Why does the same force create more pressure on a smaller area?
答案
Pressure is inversely proportional to area for fixed perpendicular force. Concentrating the force raises F/A.
卡片 375
问题
A sample has mass 0.60 kg and volume 2.0×10⁻⁴ m³. What is its density?
答案
3.0×10³ kg/m³. Divide mass by volume.
卡片 376
问题
What conservation law underlies the continuity equation for incompressible flow?
答案
Conservation of mass. Constant density turns equal mass flow into equal volume flow.
卡片 377
问题
An immersed object rests on a scale that exerts an upward support force. If weight, buoyancy, and that support are its only vertical forces, with mg ≥ F_B, how is apparent weight related to buoyant force?
答案
N = mg - F_B. Here N is the upward scale-force magnitude. The fluid supports part of the object's weight, so the scale reading is no greater than its weight under the stated condition.
卡片 378
问题
What is the SI unit of pressure?
答案
The pascal, Pa. One pascal equals 1 N/m².
卡片 379
问题
How do pressures compare at the same horizontal level in one connected static fluid?
答案
They are equal. Container shape does not change pressure at a fixed elevation.
卡片 380
问题
What does specific gravity compare?
答案
A substance's density with water's density. It is a dimensionless ratio, commonly ρ_substance/ρ_water.
卡片 381
问题
How could collecting outflow test a volume flow rate predicted from area and average normal speed?
答案
Measure collected volume over a timed interval and compare ΔV/Δt with Av. Repeat trials and include volume and timing uncertainty.
卡片 382
问题
How does the particle model distinguish a fluid from a rigid solid?
答案
Fluid particles can rearrange and flow past one another. A rigid solid resists sustained shape change.
卡片 383
问题
At equal height along the same flow path in steady, incompressible, nonviscous flow, how are pressure and speed related?
答案
The faster region has lower static pressure. Along that flow path at equal height, P + ½ρv² remains constant.
卡片 384
问题
A fully submerged object displaces 0.020 m³ of static water. Using ρ = 1000 kg/m³ and g = 10 m/s², what is F_B?
答案
200 N. F_B = ρgV = 1000×10×0.020.
卡片 385
问题
Why can a steel ship float even though steel is denser than water?
答案
Its hollow shape makes the ship's overall average density less than water. It displaces enough water for buoyant force to balance weight.
卡片 386
问题
How does an ideal hydraulic lift with a confined incompressible fluid at rest multiply force?
答案
Equal pressure change gives F₁/A₁ = F₂/A₂. The larger-area piston produces the larger force.
卡片 387
问题
For steady, incompressible, nonviscous efflux with negligible losses, what graph can test Torricelli's relation while fluid head h varies?
答案
Graph v² versus h. With both locations open to atmospheric pressure and upper-surface speed negligible, the model predicts slope 2g.
卡片 388
问题
What does incompressible mean in the introductory ideal-fluid model?
答案
A fluid element's density stays effectively constant as it moves. Its volume does not appreciably shrink under pressure changes.
卡片 389
问题
At two points along the same flow path in steady, incompressible, nonviscous flow, how are pressure and height related when speed is equal?
答案
Pressure is lower at the higher point. P + ρgy remains constant.
卡片 390
问题
How can water displacement measure an irregular solid's volume?
答案
Submerge it fully and measure the increase in displaced-water volume. The volume change equals the submerged solid's volume if no water enters it.
卡片 391
问题
Two equal-volume samples have densities ρ and 3ρ. How do their masses compare?
答案
The denser sample has three times the mass. From m = ρV, mass scales with density at fixed volume.
卡片 392
问题
How can scale readings in air and water determine buoyant force?
答案
Subtract the immersed scale reading from the air reading. When the object is at rest and air buoyancy is negligible, the decrease equals the liquid's buoyant force.
卡片 393
问题
Static water has ρ = 1000 kg/m³. Using g = 10 m/s², what gauge pressure is 3 m below its open surface?
答案
30,000 Pa. P_gauge = ρgh = 1000×10×3.
卡片 394
问题
During steady incompressible outflow, why can a large tank's top-surface speed be neglected compared with outlet speed?
答案
The tank's surface area is much larger than the outlet area. Continuity then makes the top-surface speed much smaller.
卡片 395
问题
For a chosen fluid element in a horizontal region, what can a pressure difference do?
答案
It creates a net pressure force from higher pressure toward lower pressure and can accelerate the element by Newton's second law. Other forces must also be included when they matter.
卡片 396
问题
How can buoyancy measurements in a static fluid of known uniform density determine an irregular object's volume?
答案
Measure buoyant force while the object is fully submerged, then use V = F_B/(ρ_fluid g). The fluid density must be uniform over the displaced volume.
卡片 397
问题
A 200 N perpendicular force acts on area 0.040 m². What pressure does it create?
答案
5,000 Pa. P = F/A = 200/0.040.
卡片 398
问题
Why doesn't a hydraulic lift multiply energy?
答案
The large-force piston moves a shorter distance. Ideally, input work equals output work.
卡片 399
问题
A large open tank has steady, incompressible, nonviscous efflux with negligible losses. Using g = 10 m/s², what speed leaves an opening 5 m below the surface when upper-surface speed is negligible?
答案
10 m/s. Both locations are at atmospheric pressure, so v = √(2gh) = √100.
卡片 400
问题
An object floats first in water and then in a denser liquid. How does its submerged fraction change?
答案
It decreases in the denser liquid. Less displaced volume is needed to provide the same buoyant force.

An orange sphere traces an orbital path between a wave, a rotating disc, and a fluid ripple on a dark grid.

400张卡片