North Carolina Science Grade 7

Chapter 14: Work and Simple Machines

Calculating Power

1.
You do 300 J of work in 15 s. How much power do you use?
A)22 W
B)18 W
C)20 W
D)25 W
2.
A battery does 147 J of work in 3.5 s. How much power do you use?
A)42 W
B)40 W
C)45 W
D)48 W
3.
You do 450 J of work in 25 s. How much power do you use?
A)20 W
B)18 W
C)22 W
D)32 W
4.
A car stereo does 300 J of work in 6 s. How much power do you use?
A)50 W
B)48 W
C)45 W
D)40 W
5.
You do 420 J of work in 20 s. How much power do you use?
A)19 W
B)25 W
C)27 W
D)21 W
6.
A toaster does 1125 J of work in 2.5 s. How much power do you use?
A)400 W
B)420 W
C)450 W
D)350 W
7.
You do 1500 J of work in 60 s. How much power do you use?
A)35 W
B)25 W
C)29 W
D)32 W
8.
A streetlight does 4800 J of work in 60 s. How much power do you use?
A)100 W
B)90 W
C)80 W
D)120 W
9.
A human brain does 700 J of work in 35 s. How much power do you use?
A)20 W
B)120 W
C)200 W
D)250 W
10.
A human heart does 90 J of work in 45 s. How much power do you use?
A)4 W
B)2 W
C)10 W
D)12 W
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