When a ball is held in the air, it has potential energy. Potential energy is energy that is stored or "hidden in some way. When the ball is dropped, the potential energy is converted to kinetic energy. As the ball moves through the air, the air gives resistance. Resistance makes some of the kinetic energy inside the ball convert into heat, therefore slowing down the ball. When a ball bounces, it means that very little of the kinetic energy inside was lost. Then the ball would hit the ground, deform for a moment, and bounce up as it snaps back into shape. This ties into Newton's Third Law of Motion- every action has an equal and opposite force. This is because when a ball falls down, it has energy and pushes against the floor when it hits. The floor pushes back equally as hard and creates the deformation, snap, and bounce. However, sometimes all the energy in a falling object is lost to sound, heat, light, or something else. Then, the object will not have any force when it hits the ground and therefore will not bounce. The more energy is lost during a drop, the less an object will bounce. Finally, comes the bounce. The first bounce will be the highest, because the least amount energy has been lost. After the ball reaches its highest bounce point, it will repeat the bounce process (resistance, energy loss, deformation, snap, etc.) until it eventually loses all of its energy and stops.
Bouncing Balls by Edward Willet- http://edwardwillet.com/columns/bouncingballs.htmFriction Basics- http://www.physics4kids.com/files/motion_friction.html
Momentum Basics- http://www.physics4kids.com/files/motion_moment.htmlNewton's Laws of Motion- http://www.physics4kids.com/files/motion_laws.html