Quiz Chapter 15

Question 1: Suppose you walk across a room carrying a bucket of water in your right hand. To keep the water from sloshing out, you walk at a constant speed, making sure the bucket is kept at the same height above the ground. Which statement is true?

• a) You exert a force on the bucket and do work on the bucket as you carry it.
• b) You exert a force on the bucket but do no work on the bucket.
• c) You don’t exert a force on the bucket and you do no work on it.

Answers: b Question 2:

TRUE or FALSE:

If an object moves from one point in space to another, then work has been done on the object.

• a) TRUE
• b) FALSE Answers: b

Question 3: Suppose you push on a heavy table and the table doesn’t move.

The work that you do is

• a) positive.
• b) zero.
• c) negative.

Answers: b

Question 4: A hockey puck slides across the ice and eventually comes to a stop.

Which statement is true?

• a) The work done by gravity is zero.
• b) The work done by gravity is equal to the gravitational force times the distance the puck slides.
• c) The work done by gravity cannot be calculated.

Answers: A

Question 5: You lift a book bag straight upwards off the floor.

Which statement is correct?

• a) You do the same work whether you lift the book bag quickly or slowly.
• b) You exert the same power whether you lift the book bag quickly or slowly.
• c) The work you do is zero, making the power also zero.

Answers:A

Question 6: Any object that has kinetic energy must be

• a) moving.
• b) falling.
• c) high above the ground.
• d) at rest.

Answers: A

Question 7: A book is at rest on a tabletop. One student calculates the potential energy as 15 J. Another student calculates the potential energy as 20 J.

Which statement is correct?

• a) One or both of the students must have calculated the potential energy incorrectly.
• b) Both answers could be correct.
• c) Both answers are wrong because they use the wrong units.

Answers: b

An object that moves faster has greater potential energy.

• a) TRUE

• b) FALSE

Answers: b

Question 9: A ball is thrown straight up into the air (with no air resistance).

Where is the ball’s potential energy the greatest?

• a) When it is first released

• b) Halfway up

• c) At its highest point

Answers: c

As the ball rises, we know that

• a) the kinetic energy increases as the potential energy decreases.

• b) the kinetic energy decreases as the potential energy increases.

• c) the kinetic energy and potential energy both increase.

• d) the kinetic energy and potential energy both decrease.

Answers: b

A small fly can have a bigger momentum than a large truck

• a) TRUE

• b) FALSE

Answers: a

Question 12: You and a friend stand on ice skates facing each other in the middle of a frozen pond.

If you throw a basketball to your friend who happens to weigh less than you do, what happens?

• a) You and your friend both move away from each other at the same speed.

• b) Your friend moves away from you at a faster speed than you have.

• c) Your friend moves away from you at a slower speed than you have.

• d) You don’t move but your friend moves away at a very fast speed.

Answers: b

After you hit the ball, the rope wraps around the pole as the ball circles it with a shorter radius each time it goes around. Which of the following statements is correct about the ball after it is hit?

• a) Both the angular momentum and the speed of the ball increase.

• b) Both the angular momentum and the speed of the ball decrease.

• c) The angular momentum of the ball stays constant while the speed of the ball increases.

• d) The angular momentum of the ball stays constant while the speed of the ball decreases.

Answers: c

• a) decreases.

• b) increases.

• c) stays the same.

Answers: b

• a) The person standing on the ground sees the rocket looking “compressed” along the direction of motion, while the person in the rocket sees the person on the ground looking “stretched.

• b) The person standing on the ground sees the rocket looking “compressed” along the direction of motion, and the person in the rocket sees the person on the ground also looking “compressed. ”

• c) The person standing on the ground sees the rocket looking “stretched” along the direction of motion, while the person in the rocket sees the person on the ground looking “compressed. ”

• d) The person standing on the ground sees the rocket looking “stretched” along the direction of motion, and the person in the rocket sees the person on the ground also looking “stretched. ”

Answers: b