This force of kinetic friction F k F_k Fk​F, start subscript, k, end subscript always opposes the sliding motion and tries to reduce the speed at which the surfaces slide across each other. For example, a person sliding into second base during a baseball game is using the force of kinetic friction to slow down.

Summary

• Friction is the force that opposes motion between any surfaces that are in contact. There are four types of friction: static, sliding, rolling, and fluid friction.
• Static, sliding, and rolling friction occur between solid surfaces.
• Fluid friction occurs in fluids, which are liquids or gases.

When the mass is not moving, the object experiences static friction. The friction increases as the applied force increases until the block moves. After the block moves, it experiences kinetic friction, which is less than the maximum static friction.

The Force of Static Friction keeps a stationary object at rest! Once the Force of Static Friction is overcome, the Force of Kinetic Friction is what slows down a moving object!

Kinetic friction is less than the static friction because in kinetic friction one object is in moving condition & there is less inter molecular attraction b/w the objects whereas in static friction there is relative motion & thus there is much more inter molecular attraction & this is only why we need less force to …

Rolling Friction

Friction between moving engine parts increases their temperature and causes the parts to wear down. Friction can be both harmful and helpful, so it may be necessary to decrease or increase friction. How can we reduce friction?

(i) Nature of the surfaces in contact i.e. whether surface is rough or smooth. Friction depends on the smoothness or roughness of the two surfaces which are in contact. A rough surface produces greater friction as compared to a smooth surface.