Tennessee Science Grade 7

Chapter 14: Work and Simple Machines

Calculating Efficiency

1
You do 222 J of work pushing a box up a ramp. If the ramp does 200 J of work, what is the efficiency of the ramp?
A)90%
B)82%
C)75%
D)96%
2
You do 15,000 J of work with a screw jack. If the screw jack does 14,500 J of work, what is the efficiency of the screw jack?
A)97%
B)88%
C)75%
D)55%
3
You do 1200 J of work with gears. If the gears do 1000 J of work, what is the efficiency of the gears?
A)83%
B)75%
C)77%
D)89%
4
You do 50 J of work with a lever. If the lever does 45 J of work, what is the efficiency of the lever?
A)90%
B)85%
C)95%
D)97%
5
You do 1260 J of work with a wheel and axle. If the wheel and axle does 1200 J of work, what is the efficiency of the wheel and axel?
A)95%
B)88%
C)84%
D)97%
6
You do 75 J of work with a wedge. If the wedge does 65 J of work, what is the efficiency of the wedge?
A)87%
B)90%
C)92%
D)95%
7
You do 42 J of work with scissors. If the scissors do 40 J of work, what is the efficiency of the scissors?
A)95%
B)75%
C)78%
D)80%
8
You do 400 J of work with a pulley. If the pulley does 380 J of work, what is the efficiency of the pulley?
A)95%
B)90%
C)77%
D)98%
9
You do 260 J of work pushing a box up a ramp. If the ramp does 200 J of work, what is the efficiency of the ramp?
A)77%
B)73%
C)83%
D)85%
10
You do 280 J of work with a pulley. If the pulley does 275 J of work, what is the efficiency of the pulley?
A)98%
B)95%
C)92%
D)70%
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