When a ball is dropped, its bouncing motion never continues indefinitely; every ball eventually comes to a complete stop. Understanding why a bouncing ball ultimately ceases its motion involves exploring the transformations and dissipations of energy that occur with each interaction.
How a Ball Bounces
A ball’s bounce begins with energy transformations. When held at a height, a ball possesses potential energy due to its position. As it falls, this potential energy converts into kinetic energy, the energy of motion. Just before impact, most potential energy has transformed into kinetic energy.
Upon striking the ground, the ball and the surface temporarily deform. The ball’s elastic material compresses, storing some kinetic energy as elastic potential energy, similar to a compressed spring. As the ball attempts to return to its original shape, this stored energy converts back into kinetic energy, propelling the ball upwards.
Energy Loss During Impact
Despite the energy transformations that enable a bounce, a ball never returns to its original height due to energy loss during each impact. This loss occurs because the collision is not perfectly efficient; not all kinetic energy is converted back into the energy needed for upward motion. A significant portion of the ball’s kinetic energy is dissipated into other forms.
Primary energy loss occurs through heat generation. Internal friction within the ball’s material and at the contact point converts kinetic energy into thermal energy. Sound produced by the impact is another form of energy dissipation. Some energy is also absorbed by minor changes or vibrations within the ball or surface. Air resistance contributes to energy loss during flight, though its effect is less significant than impact losses.
The Path to Stillness
The cumulative effect of energy loss with each bounce leads to the ball’s eventual stillness. With every successive impact, a portion of the ball’s kinetic energy is converted into non-recoverable forms like heat and sound. This progressively reduces the kinetic energy available for the rebound. Consequently, the ball cannot reach the same height as the previous bounce, resulting in smaller and shorter bounces.
This reduction in energy continues until the remaining kinetic energy is insufficient to overcome gravity and lift the ball. The material properties of the ball, such as its elasticity, and the characteristics of the bouncing surface significantly influence how quickly this process occurs. Highly elastic materials and hard surfaces allow for more efficient energy transfer, leading to more bounces and higher rebounds, while less elastic materials or softer surfaces absorb more energy, causing the ball to stop more quickly.