Introduction
Conservation of energy - one of the fundamental rules of the
universe. It is actually hard to fathom a universe where
energy could be created and destroyed. In order to teach this
concept to physics students, it is popular to use something
that they are all familiar with, such as a ball on a ramp, or
a roller coaster on a track.
Revision World. Transferring Energy. Digital image. Revision World. Edexcel, n.d. Web. 11 Apr. 2015.
But that's the classic "spherical cows in a vacuum" example. The real world has air, and while people don't have to worry about that when they walk around, a vehicle that has 440 Joules per kilogram of potential energy (as in the above diagram) is not going to have all of that energy when it gets to the bottom of a hill. But how much does it lose? The answer to that is not as simple as it would seem, which is why we often simplify the problem to discount air.