Question 1

An object in motion will continue in motion with

Accepted Answer

A) acceleration. 
B) impulse. 
C) momentum. 
D) all of the above 
E) none of the above

Question 2

A car moving at 50 km/h skids 20 m with locked brakes. How far will it skid if its initial speed is 150 km/h?

Accepted Answer

A) 20 m 
B) 60 m 
C) 90 m 
D) 120 m 
E) 180 m

Question 3

A bow is drawn so that it has 40 J of potential energy. When the arrow is fired its kinetic energy is ideally

Accepted Answer

A) less than 40 J. 
B) more than 40 J. 
C) 40 J.

Question 4

It takes 40 J to push a large crate 4 m across a floor. The force exerted on the crate is

Accepted Answer

A) 4 N. 
B) 10 N. 
C) 40 N. 
D) 160 N. 
E) 1600 N.

Question 5

Give two explanations of why a cannonball fired from a long-barrel cannon will have a greater velocity than from a shorter cannon.

Accepted Answer

The answer of Give two explanations of why a cannonball...

Question 6

It is correct to say that impulse is equal to

Accepted Answer

A) momentum. 
B) the change in momentum. 
C) the force multiplied by the distance the force acts. 
D) all of the above 
E) none of the above

Question 7

When a 100-kg astronaut ejects 0.1 kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is

Accepted Answer

A) 50 m/s. 
B) 5.0 m/s. 
C) 0.5 m/s. 
D) 0.05 m/s.

Question 8

A 50-kg sack is lifted 2 m in the same time as a 25-kg sack is lifted 4 m. The power expended in raising the 50-kg sack compared to the power used to lift the 25-kg sack is

Accepted Answer

A) twice as much. 
B) half as much. 
C) the same.

Question 9

A ball is projected into the air with 900 J of kinetic energy that is transformed to potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is

Accepted Answer

A) less than 900 J. 
B) more than 900 J. 
C) 900 J. 
D) not enough information

Question 10

Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 s. How much power does the elevator use?

Accepted Answer

A) 20 W 
B) 50 W 
C) 100 W 
D) 1000 W 
E) 20,000 W

Question 11

A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is

Accepted Answer

A) 1/2 m/s. 
B) 2/5 m/s. 
C) 5/6 m/s. 
D) 6/5 m/s. 
E) 1 m/s.

Question 12

Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two-ball system?

Accepted Answer

A) 0 kg∙m/s 
B) 10 kg∙m/s 
C) not enough information

Question 13

A hydraulic press properly arranged, like a simple lever, is capable of multiplying energy input.

Accepted Answer

A) true 
B) sometimes true 
C) false

Question 14

Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard. Immediately after landing on the skateboard, Freddy's speed

Accepted Answer

A) increases. 
B) decreases. 
C) doesn't change.

Question 15

According to the impulse-momentum equation Ft = change in mv, a bungee jumper in fall has momentum which is reduced by the force F exerted by the bungee cord. If m is the mass of the jumper, then v in the equation is the speed of the

Accepted Answer

A) jumper. 
B) cord. 
C) both 
D) none of the above

Question 16

You do work on an object when you lift it against gravity. How does this work relate to gravitational potential energy? If the lifted body is dropped, what becomes of this energy?

Accepted Answer

The answer of You do work on an object when...

Question 17

When you push an object a certain distance while applying twice the force, you do

Accepted Answer

A) twice as much work. 
B) four times as much work. 
C) the same amount of work.

Question 18

A dog and a mouse run along a road with the same kinetic energy. The faster runner is the

Accepted Answer

A) dog. 
B) mouse. 
C) both run at the same speed. 
D) not enough information

Question 19

A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater

Accepted Answer

A) speed. 
B) acceleration. 
C) momentum. 
D) all of the above 
E) none of the above

Question 20

An object that has kinetic energy must be

Accepted Answer

A) moving. 
B) falling. 
C) at an elevated position. 
D) at rest. 
E) none of the above

Exam 3: Momentum and Energy