Section 10.1
Energy and Work
Practice Test
1.
A sailor pulls a boat 15.0 m along a dock using a rope that makes a 45.0° angle with the horizontal. How much work does the sailor do on the boat if he exerts a force of 185 N on the rope?
a.
1.96×10
2
J
b.
2.78×10
3
J
c.
1.59×10
3
J
d.
1.96×10
3
J
Hint
2.
How much work does the force of gravity do when a 50.0-N object falls a distance of 10.0 m?
a.
5.00×10
2
J
b.
125 J
c.
98.0 J
d.
51.0 J
Hint
3.
The equation for calculating work when there is an angle between force and displacement is __________.
a.
W
=
F
/
m
b.
W
=
F
Δ
KE
c.
W
=
Fd
cos
θ
d.
W
=
Fd
Hint
4.
An airplane passenger carries a 300.0-N suitcase up the stairs, a displacement of 5.50 m vertically and 3.75 m horizontally. How much work does the passenger do?
a.
1.65×10
2
J
b.
1.13×10
3
J
c.
1.65×10
3
J
d.
2.78×10
3
J
Hint
5.
How much work does the force of gravity do on a 5.45-kg bowling ball that falls a distance of 0.755 m?
a.
71.2 J
b.
40.3 J
c.
262 J
d.
4.11 J
Hint
6.
In Figure 10-1, if the force exerted on a 3.0-kg backpack that is initally at rest is 20.0 N and the distance it acts over is 0.25 m, what is the final speed of the backpack?
a.
2.8 m/s
b.
5.0 m/s
c.
1.8 m/s
d.
3.3 m/s
Hint
7.
An electric motor lifts an elevator 14.0 m in 22.5 s by exerting an upward force of 1.75×10
4
N. What power does the motor produce in kilowatts?
a.
10.9 kW
b.
245 kW
c.
1.09×10
4
kW
d.
2.45×10
4
kW
Hint
8.
Energy is defined as __________.
a.
power
b.
motion
c.
the ability of an object to produce change in the environment or itself
d.
the effort required to perform work
Hint
9.
The unit for kinetic energy is the __________.
a.
joule
b.
volt
c.
watt
d.
ampere
Hint
10.
A 1200.0-kg car speeds up from 16.0 m/s to 20.0 m/s. How much work was done on the car to increase its speed?
a.
3.1×10
5
J
b.
8.6×10
5
J
c.
8.6×10
4
J
d.
9.6×10
3
J
Hint
11.
A forklift raises a box 2.5 m doing 8.7 kJ of work on it. What is the mass of the box?
a.
7.2×10
2
kg
b.
3.5×10
3
kg
c.
3.6×10
2
kg
d.
3.6×10
3
kg
Hint
12.
A hydrolic lift raises a 1.14×10
3
-kg car a distance of 2.4 m. If the car is lifted in 47 s, how much power does the lift produce?
a.
570 kW
b.
290 W
c.
58.2 W
d.
570 W
Hint
13.
The equation for work is __________.
a.
W
=
Fd
b.
W
=
F
/
m
c.
W
=
ma
d.
W
=
F
Δ
KE
Hint
14.
A steel ball with mass 5.0 kg is at rest on a smooth, level surface. A constant force acts on it through a distance of 10.0 m causing it to roll at 25 m/s. What is the magnitude of the force?
a.
1.6×10
2
N
b.
4.9 N
c.
6.3 N
d.
1.6×10
3
N
Hint
15.
If the boy in Figure 10-3 pushes on the car while it travels a horizontal distance of 1.1 m, how much work does he do?
a.
140 J
b.
64 J
c.
120 J
d.
58 J
Hint
16.
A 16.8-kg boy is riding in a 4.50-kg wagon. A 14.0-kg girl pushes the wagon and exerts a constant force of 2.60 N over a distance of 3.50 m. How much work does the girl do pushing the wagon?
a.
127 J
b.
0.26 J
c.
9.10 J
d.
66.4 J
Hint
17.
A 1200.0-kg car speeds up from 16.0 m/s to 20.0 m/s. What were its initial and final energies?
a.
initial 1.54×10
5
J, final 2.40×10
5
J
b.
initial 2.40×10
5
J, final 1.54×10
5
J
c.
initial 3.07×10
5
J, final 4.80×10
5
J
d.
initial 4.80×10
5
J, final 3.07×10
5
J
Hint
18.
The energy of an object resulting from motion is __________ energy.
a.
mechanical
b.
thermal
c.
kinetic
d.
potential
Hint
19.
The work-energy theorem states that __________.
a.
when work is done on an object, a change in kinetic energy results.
b.
when a machine works at 100 percent efficiency, the energy of the system remains constant
c.
when work is done at a rate of one joule per second, the power produced is one watt
d.
effort is required to resist a change in the energy of a system
Hint
20.
One __________ is one joule of energy transferred in one second.
a.
newton
b.
volt
c.
watt
d.
calorie
Hint
21.
A joule is __________.
a.
1 N·s
b.
1 N·m
c.
1 N·m/s
d.
1
F
r
/
F
e
Hint
22.
In Figure 10-1, if the force exerted on the backpack is 20.0 N and the distance it acts over is 0.25 m, what is the change in kinetic energy of the backpack?
a.
5.0 J
b.
2.5 J
c.
8.0×10
1
J
d.
4.0×10
1
J
Hint
23.
A rope is used to pull a metal box 12.0 m across the floor with a force of 456 N. The rope is held at an angle of 52.0° with the floor. How much work does the puller do?
a.
3.37×10
3
J
b.
5.47×10
3
J
c.
4.31×10
3
J
d.
3.37×10
2
J
Hint
24.
A student lifts a box of books that weighs 215 N. The box is lifted 1.75 m. How much work does the student do on the box?
a.
376 J
b.
123 J
c.
217 J
d.
38.4 J
Hint
25.
Which of the following has the greatest kinetic energy, a 35.0-g bullet traveling at 1.20×10
3
m/s, a 35.0-kg cheetah running at 30 m/s, an 875-kg car traveling at 5 m/s, or a 148-g pitched baseball moving at 45 m/s?
a.
bullet
b.
cheetah
c.
car
d.
baseball
Hint
26.
A rifle can shoot a 4.20-g bullet at a speed of 965 m/s. What is the kinetic energy of the bullet as it leaves the rifle?
a.
1.96×10
3
J
b.
2.03 J
c.
1.96×10
6
J
d.
2.03×10
3
J
Hint
27.
A student lifts a box of books that weighs 215 N. The box is lifted 1.75 m. What is the change in energy of the box?
a.
38.4 J
b.
123 J
c.
225 J
d.
376 J
Hint
28.
If you exert a force on an object in the direction opposite to its motion, the kinetic energy of the object __________.
a.
remains constant
b.
increases
c.
is zero
d.
decreases
Hint
29.
A 16.8-kg boy is riding in a 4.50-kg wagon. A 14.0-kg girl pushes the wagon and exerts a constant force of 2.60 N over a distance of 3.50 m. What is the change in energy of the boy and the wagon?
a.
25.5 J
b.
47.6 J
c.
12.8 J
d.
9.10 J
Hint
30.
__________ is the rate of doing work.
a.
Effort
b.
Force
c.
Power
d.
Energy
Hint
