200
Jennifer, who weighs 450 newtons, and Judy, who weighs 600 newtons, are standing at the bottom of a flight
of stairs that is 4.00 meters high. Jennifer runs up the stairs in 3.0 seconds. Judy runs up the same stairs in 4.0
seconds. Compare the work done and the power generated by each girl's run up the stairs. Support your
answer by showing calculations for each quantity.
a. Who does more work?
b. Who is more powerful?
What is
Judy does more work. She does 2,400 joules of work.
work = force × distance
work = 600 N × 4.00 m
work = 2,400 J
Jennifer does only 1,800 joules of work
work = force × distance
work = 450 N × 4.00 m
work = 1800 J
The girls generate the same amount of power:
power = work ÷ time
For Judy,
power = 2,400 J ÷ 4.0 s
power = 600 watts
For Jennifer,
power = 1,800 J ÷ 3.0 s
power = 600 watts