Question

Natalie lifts a 15-kg rock from the ground onto a 1.5 meter high wall. what is the amount of potential energy she has given the rock?

Answer 1

The amount of gravitational potential energy acquired by the rock is equal to:
$\Delta U = mg \Delta h$
where 
m is the mass of the rock
g is the gravitational acceleration
$\Delta h$ is the increase in height of the rock

Substituting the data of the problem, we find
$\Delta U=(15 kg)(9.81 m/s^2)(1.5 m)=220.7 J$
So, Natalie gave 220.7 J of energy to the rock.