# Glencoe Science Level Blue

## Chapter 20: Work and Simple Machines

### Calculating Power

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