Question

A mass of 3kg hangs 2m above the ground.what is the gravitational potential energy of the mass-earth system at
(1)the ground
(2) a height of 3m above the ground
(3) a height of 4m

Answer 1

1)

$$E=mgh=(3)(10)(0)=0\ J$$

2)

$$E=mgh=(3)(10)(3)=90\ J$$

3)

$$E=mgh=(3)(10)(4)=120\ J$$