- Joined Aug 27, 2009
It is relatively common on Physics Forums to see arguments that are effectively similar to the following: When we jump off the ground, the ground does not move. Because of this, the force from the ground on us does zero total work. Since the force does no work, we cannot gain any kinetic energy. We therefore cannot jump off the ground. Now, the conclusion here is obviously false. The world high jump record is 2.45 meters, definitely larger than zero. So where did the energy come from? This Insight seeks to clarify this in a fairly accessible way.