Question

A 10-kg rock falls from a height of 8.0 m above the

ground. What is the potential energy of the rock?

Answer 1

Well you should know that he equation for potential energy is PE= mgh (mass x gravitational acceleration x height).
The mass of the rock is 10 kg, the height is 8 m and the gravitational acceleration on earth is ALWAYS constant (9.8m/s^2). So this is what you do:
PE= 10 x 9.8 x 8
PE= 784 Joules.