Question

What is the gravitational potential energy of a ball with a weight of 72 N when it is sitting on a shelf 1.4 m above the floor?

Answer 1

First you must convert the weight to mass. So:

W = mg (assuming that gravity is 9.8 Nkg-1)

m = W/g
= 72 / 9.8
= 7.3kg

Then we can use Ep = mgh

= 7.3*9.8*1.4

= 100.1N