Potential energy of a 1200 kg boulder on a cliff 45 m above the ground

Potential Energy (PE) is found using the equation mgh, where

m = mass,

g = force of gravity,

h = height

Since we are using the metric system, our force due to gravity will be 9.8m/s^2. Plug in what we know, and we get

(1200kg) (45m) (9.8m/s^2) = PE

Multiply those three variables together, and you will get your potential energy, in Joules! Good luck!