Section 4: Matter and Energy
The Characteristics of Contact Forces

Friction is a force. It slows motion and impedes flows of energy. It also produces thermal energy, something you can demonstrate by rubbing your hands together. If you rub your hands briskly, you’ll feel warmth almost right away. If you recall the bouncing ball from an earlier section, impact with the ground caused deformation of the ball due to its elasticity, while friction (as well as air resistance and gravitational forces) caused each successive bounce of the ball to be lower. Friction is a mechanism of energy transfer: “Each time the ball hits the ground there is noise, vibration and energy transfer into the floor that takes energy from the ball” (Haby, n.d., par. 3).

In physics, a contact force acts at the point at which two objects come into contact with each other. You have just finished reading about frictional force, which is one of the six different contact forces:

Click the link below to learn more about these six contact forces.