Chapter 5:
Work and Machines
Practice Test
1.
You exert a force of 500 N on a machine over a distance of 0.3 m. If the machine is 100% efficient and moves an object a distance of 0.5 m, how much force does the machine exert on the object?
a.
300 N
b.
500 N
c.
250 N
d.
833 N
Hint
2.
What power is used by a machine to perform 800 J of work in 25 s?
a.
20,000 W
b.
32 W
c.
1.28 W
d.
0.03125 W
Hint
3.
How much work is needed to lift a 20 kg box up to a shelf 2 m high?
a.
392 J
b.
196 J
c.
10 J
d.
40 J
Hint
4.
What is the IMA of a wheel with a radius of 0.35 m and an axle radius of 0.04 m?
a.
0.31
b.
1.14
c.
0.39
d.
8.75
Hint
5.
When moving a couch, you exert a force of 400 N and push it 4 m. How much work have you done?
a.
400 J
b.
1600 J
c.
4 J
d.
100 J
Hint
6.
How much energy do you save per hour if you replace a 60 watt light bulb with a 55 watt light bulb?
a.
300 J
b.
18,000 J
c.
5 J
d.
3600 J
Hint
7.
What is the efficiency of a machine if you do work on the machine at a rate of 1200 W and the machine does work at a rate of 400 W?
a.
33.3%
b.
300%
c.
100%
d.
48%
Hint
8.
Suppose you supply energy to a machine at a rate of 700 W and that the machine converts 560 J into heat every second. At what rate does the machine do work?
a.
560 W
b.
700 W
c.
1260 W
d.
140 W
Hint
9.
What is the IMA of a see-saw with a 1.6 m effort arm and a 1.2 m resistance arm?
a.
2.8
b.
0.4
c.
0.75
d.
1.33
Hint
10.
An inclined plane has an IMA of 2.5 and a height of 3.0 m. How long is this inclined plane?
a.
7.5 m
b.
1.2 m
c.
0.5 m
d.
5.5 m
Hint
