I lift a 20kg ball up 2.5 meters off the ground on Earth. -Earth’s gravitational acceleration is about 9.8 m/s2.

How much gravitational potential energy does the ball have at this point?
How much work did I do lifting up the ball?
If I lift the same ball the same distance on the Moon, then how much gravitational potential energy will it have? (Moon’s Gravity = 1.6 m/s2)

How much gravitational potential energy does the ball have at this point? At h = 20.4 m the gravitational potential energy of the ball reaches maximum.  

How much work did I do lifting up the ball?  As you are lifting the object you are doing work on the object. The work W done on an object by a constant force is defined as W = F·d. It is equal to the magnitude of the force, multiplied by the distance the object moves in the direction of the force.

c. magnitude and direction