It sure does. Newton's first law of motion says that
anything keeps going at the same speed in the same direction unless
something exerts a force on it. So a tennis ball can't bounce unless
something - a racquet, the ground, a wall- exerts a force on it.
you might wonder why some balls bounce more than others. Tennis balls
usually bounce well, but lumps of clay usually don't bounce much at
all. You could describe the reasons in terms of forces, but it is
actually easier to describe in terms of energy.
When a nice
springy tennis ball hits a wall, it squashes like a spring. The kinetic
energy that it had when it was moving mostly goes into a type of
potential energy of the squashed tennis ball. For a tennis ball, that
gets a little complicated to describe, but
for a bouncy solid
superball, the energy goes into compressing, stretching, and bending
spring-like molecules. As the ball springs back to its round shape most
of that energy comes back into the ball's motion. Some goes away as
sound, or into slightly heating up
the molecules in the tennis ball.
a lump of clay hits a wall, it also squashes. However, a squashed lump
of clay doesn't spring back. As the molecules in the clay slid past
each other, while it squashed, the friction between them heated them
up. Most of the energy got dumped into heating up the clay, leaving
little for its return bounce.
(republished on 07/11/06)