Workshop 2

4. Gravitational Potential Energy

All matter on or near the surface of the Earth has the potential to fall to a lower level if permitted. When a force raises an object, the object receives more gravitational potential energy. When the object drops, it releases some of this stored potential energy. Potential energy, therefore, tells us about stored, or latent, capacity to do work.

When we lift a ball off the surface of the table, our work is giving it gravitational potential energy. Once we release it, the ball falls, and as it descends, its potential energy is converted into kinetic energy — the energy of motion. When the ball hits the table, the table, in turn, impacts the surface of the ball. Some of that kinetic energy generates a force that causes the ball (an elastic object) to flatten. The faster the ball is moving when it hits — that is, the more kinetic energy it has — the greater the force exerted on it, and the flatter the ball will become on impact. Since, in this case, the kinetic energy depends on how high we are holding the ball when we release it, a ball dropped from higher up will flatten more upon impact.

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