Amotor with a power of 7.0 × 104 watts lifts a loaded elevator to a height of 20.00 meters for 40 seconds. what is the force exerted by the motor on the elevator?

Explanation:

First of all, we can find the work done as follows:

where P is the power and t is the time taken. In this problem, and , so the work done is

The work done is equal to the force applied F times the displacement d:

since we know d=20.0 meters, we can re-arrange the equation to find the force exerted:

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).