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AP Physics 1 · Unit 3 · Energy

Work and Kinetic Energy Practice Problems

Calculate work by individual forces and relate net work to a change in kinetic energy. Practice lifts, steady towing, braking, angled pushes, and carts that are already moving.

12 questions6 conceptual · 6 calculation

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Simulation scene from the Work and Kinetic Energy lesson.Open interactive practice
A scene from the related lesson. Open the practice to work through the questions.

What you’ll practice

Connect a force acting over distance with energy change

Determine the work of each force

Use force magnitude, displacement, and the angle between them. Identify zero work when displacement is zero or the force is perpendicular to motion.

Use the work–energy theorem

Find a speed change from net work or calculate the resisting force needed to stop an object. Include its initial kinetic energy.

Combine work from several interactions

Account for motor pulls, friction, gravity, and angled pushes. Explain how positive and negative individual work can sum to zero.

A question from this set

Strong pulls without movement

Two people pull equally hard in opposite horizontal directions on a crate, and the crate does not move. During this interval, how much mechanical work does each pulling force do on the crate?

  • Each does positive work because the people are exerting effort.
  • Each does zero work because the crate has no displacement.
  • One does positive work and the other negative work even though the crate stays still.
Try it in the practice set
Strong pulls without movementTwo people pull equally hard in opposite horizontal directions on a crate, and the crate does not move. During this interval, how much mechanical work does each pulling force do on the crate?CratePullPullNo movement during the interval
Equal opposing pulls keep the crate stationary during the interval.

Key ideas

Work depends on displacement as well as force

Use W = Fd cos θ for a constant force

The angle is between the force and displacement. A force along the motion does positive work; an opposing force does negative work.

Net work equals the kinetic-energy change

Add the work of all forces to find ΔK. Kinetic energy is ½mv², so doubling speed multiplies kinetic energy by four.

See the physics

Compare displacement with the energy record

Check your response, then run a lift, tow, brake, or balanced-pull scene. Compare each force’s work and the net kinetic-energy change with the values you calculated.

Use a hint for a starting point or open a worked solution to follow the reasoning. Your progress saves in this browser, so you can return to unfinished questions.

Ready for work and kinetic energy?

Begin with a conceptual question, then work through the calculations.

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