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AP Physics C: Mechanics Practice Quiz: Work

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 10 questions to check your progress.

Question 1 of 10

According to the provided definition, what does work represent in a physical system?

All Questions (10)

According to the provided definition, what does work represent in a physical system?

A) The total energy contained within the system.

B) The rate at which energy is transferred.

C) The transfer of energy into or out of a system by a force.

D) The potential energy stored in a system due to its position.

Correct Answer: C

The content explicitly states, "Work is the amount of energy transferred into or out of a system by a force exerted on that system over a distance."

If the net work done on an object is positive, what can be concluded about the object's kinetic energy?

A) The kinetic energy has increased.

B) The kinetic energy has decreased.

C) The kinetic energy remains constant.

D) The kinetic energy is zero.

Correct Answer: A

The work-energy theorem, ΔK = ΣWi, states that the change in kinetic energy (ΔK) is equal to the net work done. If the net work is positive, ΔK is positive, meaning the final kinetic energy is greater than the initial kinetic energy.

An object is moving at a constant velocity. What is the net work done on the object?

A) Positive, as a force is required to maintain motion.

B) Negative, due to air resistance.

C) Zero, because the kinetic energy is not changing.

D) It cannot be determined without knowing the object's mass.

Correct Answer: C

According to the work-energy theorem, ΔK = ΣWi. If the velocity is constant, the kinetic energy is also constant. Therefore, the change in kinetic energy, ΔK, is zero, which means the net work done on the object must also be zero.

Which of the following expressions correctly calculates the work done on an object by a force that varies with position?

A) W = F × d

B) W = ΔK / t

C) W = ∫[a, b] F⃗(r) ⋅ dr⃗

D) W = m ⋅ a ⋅ d

Correct Answer: C

The provided content explicitly states that "The work done on an object by a variable force is calculated using W = ∫[a, b] F⃗(r) ⋅ dr⃗."

A student pushes against a stationary brick wall with a constant force. How much work does the student do on the wall?

A) A positive amount, equal to the force times the time.

B) A negative amount, as the wall exerts an equal and opposite force.

C) Zero, because the wall does not move.

D) It cannot be determined without knowing the student's mass.

Correct Answer: C

Work is defined as energy transferred by a force exerted over a distance. Since the wall does not move, the displacement (dr⃗) is zero, and therefore no work is done on the wall, regardless of the force applied.

A block is pulled across a rough horizontal surface, and its speed decreases. Which statement accurately describes the work done on the block?

A) The net work done on the block is positive.

B) The work done by the pulling force must be zero.

C) The net work done on the block is negative.

D) The work done by friction must be positive.

Correct Answer: C

The work-energy theorem states ΔK = ΣWi. Since the block's speed decreases, its kinetic energy decreases, meaning ΔK is negative. Therefore, the net work (the sum of all work done by all forces) on the block must be negative.

In the formula W = ∫[a, b] F⃗(r) ⋅ dr⃗, what is the physical significance of the dot product (⋅)?

A) It ensures that only the component of force perpendicular to the displacement contributes to the work.

B) It calculates the total magnitude of the force vector at all points.

C) It ensures that only the component of force parallel to the displacement contributes to the work.

D) It represents the simple multiplication of the force and displacement magnitudes.

Correct Answer: C

The dot product of two vectors, A⃗ ⋅ B⃗, multiplies the magnitude of one vector by the component of the second vector that is parallel to the first. In the work integral, F⃗(r) ⋅ dr⃗ means that only the component of the force vector F⃗ that is parallel to the infinitesimal displacement vector dr⃗ does work.

Which of the following scenarios describes a situation where negative work is done by the force of friction on an object?

A) The force of friction on a car's tires as it accelerates from rest.

B) The force of friction on a box at rest on an incline.

C) The force of friction on a hockey puck sliding to a stop on ice.

D) The force of friction is always zero, so it can do no work.

Correct Answer: C

Work is the transfer of energy by a force. Negative work is done when the force is in the opposite direction of the displacement. The force of kinetic friction always opposes the direction of motion. Therefore, the work done by friction on the sliding puck is negative.

The work-energy theorem directly relates the net work done on an object to which of the following quantities?

A) The object's change in potential energy.

B) The object's change in kinetic energy.

C) The total impulse delivered to the object.

D) The object's final momentum.

Correct Answer: B

The content explicitly states, "The work-energy theorem states that the change in an object's kinetic energy is equal to the sum of the work (net work) being done by all forces exerted on the object." The relevant equation is ΔK = ΣWi.

When work is done on a system by a collection of forces, the sum of the work done by each individual force is known as the:

A) Potential work.

B) Kinetic work.

C) Total force.

D) Net work.

Correct Answer: D

The work-energy theorem is defined in terms of the "sum of the work (net work) being done by all forces exerted on the object," which is represented by ΣWi. This sum is called the net work.