Question

Explain Ep = mgh

Answer 1

That is the formula for potential energy. Potential energy, at least in mechanics, is usually converted into motion, and thus kinetic energy. So the mass times the gravity times the height is how much kinetic energy it COULD (potentially) have.

Answer 2

Think about work, too.

Work is the force times the displacement in the direction of the force.

The force is weight (gravitational). So it is \(mg\).

Now, the direction of the force of gravity is downward. So the displacement in that direction is either downward or upward (just opposite directions). The displacement that it could potentially have defines the displacement that you'll want to use for the potential energy. This displacement can be seen as the "height," or \(h\).