A stonemason lifts a small boulder weighing Fw = 80 N from the ground onto a height = 1.50 m wall in the time t = 2.0 s.

Question

Using the values in the problem, calculate how much work she does.

What power does she develop in watts?

What power does she develop in kilowatts?

What power does she develop in horsepower?

Answer 1

work = force * distance in direction of force
= 80 * 1.5 = 120 Joules

power
Hey we know that cold by now
= 120 Joules / 2 seconds = 60 Watts

60 watts * 1 kw/1000 watts = 0.06 kw

0.06 kw * 1.341 hp/kw = 0.08 Hp

I figure with an electric motor you get about 1 hp per kw after allowing for efficiency

Answer 2

work=force(height)
powerWatts= workJoules/timeinSec

powerKwatts=powerwatts/1000

powerHP=powerwatts/746