Chapter 7: Energy

Question 1

If you push for a half hour or a whole hour against a stationary wall: a) twice as much work is done during the half hour; b) it is impossible to determine how much work is done; c) half as much work is done during the half hour; d) no work on the wall is done in either case.

Answer 1

d) no work on the wall is done in either case.

Question 2

If you push an object a given distance, while applying twice the force, you do: a) twice as much work; b) the same amount of work; c) four times as much work; d) half as much work.

Answer 2

a) twice as much work.

Question 3

If you do work on an object in one-third the usual time, your power output is: a) three times the usual power output; b) the usual power output; c) impossible to predict without additional information; d) one third the usual power output.

Answer 3

a) three times the usual power output.

Question 4

Do 100 J of work in 50 s and your power output is

Answer 4

2 W

Question 5

An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is: a) twice as much; b) four times as much; c) half as much; d) the same.

Answer 5

a) twice as much.

Question 6

An object that has kinetic energy must be

Answer 6

moving.

Question 7

An object may have potential energy because of its: a) location; b) acceleration; c) speed; d) momentum; e) none of these.

Answer 7

a) location.

Question 8

A clerk can lift containers a vertical distance of 1 meter or can roll them up a 2 meter-long ramp to the same elevation. With the ramp, the applied force required is about

Answer 8

half as much.

Question 9

After rolling halfway down an incline, a marble’s kinetic energy is: a) the same as its potential energy; b) less than its potential energy; c) impossible to determine; d) greater than its potential energy.

Answer 9

a) the same as its potential energy.

Question 10

No work is done by gravity on a bowling ball that rolls along a bowling alley because: a) the force on the ball is at right angles to the ball’s motion; b) no potential energy is being converted to kinetic energy; c) its kinetic energy remains constant; d) no force acts on the ball; e) no distance is covered by the ball.

Answer 10

a) the force on the ball is at right angles to the ball’s motion.