Unit 4 ( Power)

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

12P

A child pulls on a wagon with a force of 75 N. If the wagon moves a total of 42 meters in 3.1 min, what is the average power delivered by the child?

17 W

At what minimum rate is a 60.0-kg boy using energy when, in 8.00 s, he runs up a flight of stairs that is 10.0-m high?

735 W

A 1500-kg car accelerates from rest to 25 m/s in 7.0 s. What is the average power delivered by the engine? ( 1 hp = 746 W)

90 hp

Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?

The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.

Jill does twice as much work as Jack does and in half the time. Jill's power output is

four times Jack's power output.