Question

I lift a 20kg ball up 2.5 meters off the ground on Earth.

Answer 1

Answer: 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.