The Relationship Between Potential Energy and Kinetic Energy

potential energy is only important in differences you can add an arbitrary number to the potential energy of a banana at the bookshelf doesn't matter. "It's very easy to see kinetic energy and potential energy sloshing back and forth into each other if you have for example a ball" he says. 'If there wasn't friction or air resistance then it would just go on forever smoothly sliding back between the two different forms of energy'