Review Questions

  1. Which of the following is NOT true of work?

    1. It is the scalar product of force and displacement.
    2. It is a vector that is always in the same direction as the force.
    3. It is measured in joules.
    4. It has the same units as energy.
    5. It takes energy to perform work.

  2. A 5 kg box is pushed across a level floor with a force of 50 N for a displacement of 10 m, then lifted to a height of 3 m. What is the total work done on the box?

    1. 250 J
    2. 500 J
    3. 650 J
    4. 2,500 J
    5. 7,500 J

  3. A 30 kg cart is pushed up the inclined plane shown by a force F to a height of 5 m.

    What is the potential energy of the cart when it reaches the top of the inclined plane?

    1. 1,500 J
    2. 630 J
    3. 600 J
    4. 300 J
    5. 150 J

  4. The work done on a system

    1. always changes the potential energy of the system.
    2. always changes the kinetic energy of the system.
    3. always changes the momentum of a system.
    4. can change either the potential energy or kinetic energy of the system.
    5. is not related to the energy of the system.

  5. A ball falls from a height h from a tower. Which of the following statements is true?

    1. The potential energy of the ball is conserved as it falls.
    2. The kinetic energy of the ball is conserved as it falls.
    3. The difference between the potential energy and the kinetic energy is a constant as the ball falls.
    4. The sum of the kinetic and potential energies of the ball is a constant.
    5. The momentum of the ball is constant as the ball falls.

  6. A 0.5 kg ball is dropped from a third-story window that is 10 m above the sidewalk. What is the speed of the ball just before it strikes the sidewalk?

    1. 5 m/s
    2. 10 m/s
    3. 14 m/s
    4. 28 m/s
    5. 200 m/s

  7. Drew lifts a 50 kg crate onto a truck bed 1 meter high in 2 seconds. Perry lifts fifty 1 kg boxes onto the same truck in a time of 2 minutes. Which of the following statements is true?

    1. Drew does more work than Perry does.
    2. Perry does more work than Drew does.
    3. They do the same amount of work, but Drew operates at a higher power level.
    4. They do the same amount of work, but Perry operates at a higher power level.
    5. Drew and Perry do the same amount of work and operate at the same power level.

  8. A crane can lift a 600 kg mass to a height of 20 m in 2 minutes. The power at which the crane is operating is

    1. 1,000 watts.
    2. 6,000 watts.
    3. 60,000 watts.
    4. 240,000 watts.
    5. 1,440,000 watts.