Chapter 4:
Work and Energy
Practice Test
1.
A student's backpack weighs 8 N. The student lifts the backpack from the floor to a table 0.5 m high. How much work is done on the backpack?
a.
4 J
b.
6 J
c.
16 J
d.
8 J
Hint
2.
What is the law of conservation of energy?
a.
Energy is conserved as it changes from one form to another.
b.
Energy can be neither created nor destroyed.
c.
The total amount of energy remains the same.
d.
All of the above are correct.
Hint
3.
What is the slingshot effect that scientists use to send space probes into the far reaches of the solar system?
a.
Potential energy is converted to thermal energy.
b.
Elastic potential energy is converted to kinetic energy.
c.
Kinetic energy is converted to thermal energy.
d.
Gravitational potential energy is converted to kinetic energy.
Hint
4.
What happens to the energy of a falling object as it accelerates toward Earth?
a.
Gravitational potential energy decreases.
b.
Kinetic energy increases.
c.
Potential energy is transformed into kinetic energy.
d.
All of the above are correct.
Hint
5.
What conditions must be met in order for work to be done?
a.
There must be motion, but force is not required.
b.
Motion must be in the direction of force for work to be done.
c.
There must be force, but motion is not required.
d.
Force and motion are all that is required.
Hint
6.
What is the kinetic energy of a 10-kg object moving at a velocity of 2 m/s?
a.
40 J
b.
10 J
c.
100 J
d.
20 J
Hint
7.
Suppose you weigh 500 N and you climb up a staircase that is 4 m high. What is your change in gravitational potential energy?
a.
200 J
b.
125 J
c.
1000 J
d.
2000 J
Hint
8.
What units are used to express gravitational potential energy?
a.
joules
b.
kilograms
c.
newtons
d.
newtons per meter
Hint
9.
When a tennis ball is dropped to the ground, it does not bounce back to its original height. Why not?
a.
Some of the potential energy of the ball has been converted to kinetic energy.
b.
Some of the potential energy of the ball has been converted to elastic potential energy.
c.
newtons
d.
All of the above are correct.
Hint
10.
Suppose Galileo drops a ball from the top of the Leaning Tower of Pisa. As the ball accelerates toward Earth it gains kinetic energy. Where does this energy come from?
a.
The energy is stored in the ball because of its position above the ground.
b.
The energy is created by the falling ball.
c.
The energy is stored in Earth.
d.
All of the above.
Hint
11.
A falling leaf eventually stops accelerating toward Earth because of wind resistance. Potential energy of the leaf is still decreasing as the leaf falls. Where is the energy going?
a.
The remaining potential energy is converted to thermal energy.
b.
The remaining potential energy is converted to mechanical energy.
c.
The remaining potential energy is converted to kinetic energy and thermal energy.
d.
The remaining potential energy is converted to kinetic energy.
Hint
12.
When is the mechanical energy of a pendulum the highest?
a.
The mechanical energy of the pendulum remains constant.
b.
when the pendulum reaches the bottom of its first swing
c.
when the pendulum is first set into motion
d.
when the pendulum has eventually stopped moving
Hint
13.
How is work stored when a spring is compressed?
a.
kinetic energy
b.
elastic potential energy
c.
when the pendulum is first set into motion
d.
All of the above are correct.
Hint
14.
What is the basic problem with constructing a perpetual motion machine?
a.
Friction produces thermal losses.
b.
The total amount of mechanical energy remains the same.
c.
People think machines are silly.
d.
Perpetual motion machines use elastic potential energy.
Hint
15.
Which of the following is an example of stored elastic potential energy?
a.
a loose spring
b.
a balloon inflated with air
c.
a falling rubber ball
d.
All of the above are correct.
Hint
