There is a rock sitting on top of a cliff that is 40 m high. The rock weighs 20 kg. What is the potential energy of the rock?

Answer: 7840 joules

Explanation:

Given that:

Potential energy of rock = ?

Mass of rock = 20 kg

Height = 40 metres

Acceleration due to gravity g = 9.8m/s2

Recall that potential energy (P. E) is the energy possessed by an object at rest. So, for the rock at rest:

P. E = Mass x Acceleration due to gravity x height

= 20 kg x 9.8m/s2 x 40 metres

= 7840 joules

Thus, the potential energy of the rock is

7840 joules