The Effect of the Cold on Basketballs

Energy and the Rebound

• When basketballs fall and hit the ground, they compress air, which stores energy in the process. The common use for that energy, particularly in warm balls, is for it to transfer back to the ball as the compressed air returns to its original characteristics, thus creating the rebound bounce.

Cold Balls and Their Reduced Bounce

• The reason for the reduction in bounciness in cold balls has to do with the concept of internal air pressure -- a ball with high internal pressure will bounce well, and a ball with low pressure will bounce poorly. In a warm ball, the internal air pressure is plentiful, ensuring that the ball will bounce as desired. When a basketball is cooled, its internal pressure falls. This is because cooling the ball reduces its thermal energy, which is what creates internal pressure. Without the thermal energy and air pressure, a ball ceases to be firm and takes on more of a "squishy" feel. A ball that was properly inflated at warm temperatures will become under-inflated if cooled, altering its reaction to hitting the ground from a springy bounce to a muted thud.

Elasticity and Heating

• The other contributing factor to why cold balls do not bounce well has to do with the elasticity of their skin at lower temperatures. The colder a basketball's material gets, the less elastic it becomes. Under these circumstances, the ball's skin begins to absorb energy to create heat rather than transferring it into the rebound. By storing energy in the skin rather than the air, the ball loses much of its ability to bounce.

Extreme Cold

• Creating a leathery, under-inflated ball which bounces poorly is the extent of the effect produced by average levels of cold on basketballs. To get any more radical effect, one would have to intentionally expose the ball to extreme cold. Taken to low enough temperatures, a basketball's skin will freeze and become brittle.