A 1.9 kg ball is attached to a ceiling by a string. The distance from the ceiling to the center of the ball is 0.81 m, and the height of the room is 3.00 m.

Question

(a) What is the gravitational potential energy associated with the ball relative to the ceiling?

(b) What is the gravitational potential energy associated with the ball relative to the floor?

(c) What is the gravitational potential energy associated with the ball relative to a point at the same elevation as the ball?

Answer 1

a) GPE = mgh

So, 1.9 x 9.8 x -0.81 = -15.0822 ≈ -15.1J

b) GPE = 1.9 x 9.8 x (3 - 0.81) = 40.78888 ≈ 40.8J

c) No height difference, so GPE = 0