If you hold a ball on a string to your face and let it go without adding extra pressure, it won't hit you. This is due to the principles of kinetic and potential energy. However, if you apply extra pressure when releasing it, the ball will swing back with enough force to hit you.

Potential energy is stored when the ball is held up. When released, it converts to kinetic energy as it moves away and then back to potential energy at the peak of its swing. When it swings back towards you, it's kinetic energy again. The ball cannot go higher than its initial drop point, so if released gently, it won't hit you on the return swing.

Potential energy is energy stored in the arrangement of an object. For example, when a bowstring is pulled back, it has potential energy. Kinetic energy is the energy an object possesses when it is in motion. When the bowstring is released, the stored potential energy converts into kinetic energy as the arrow flies.