Swing Pumping Animation

This is an animation of the way that a child pumps a swing to make it go higher. The swing's kinetic energy is increased when the child shortens the rope by pulling it toward her/him and by raising his/her lower legs at the bottom of the stroke. By doing so, the child is doing work against gravity which is then converted to kinetic energy so that the swing goes higher. The most important physics to notice is that the pushing and pulling are totally ineffective in two situations 1: When they are continuous 2: When they are applied at the ends of the swing trajectory. Some might say that the moves to increase the swing energy actually just increase the angular momentum like a spinning ice skater does. That is true but the ultimate goal is to make the high point of the center of mass of the swing higher which increases the gravitational potential energy.
Click Here for Force Equations