Explain why sliding friction is less than static friction.

Hint: Friction comes into play due to surface irregularities and adhesion.

Complete step by step solution:
Friction is the force that arises when two bodies are sliding or trying to slide across each other. It always tries to resist motion and acts in a direction opposite to that of the applied force. It arises due to roughness, deformation or adhesion in surfaces. Static friction is experienced when there is no relative motion between the two bodies and sliding friction is experienced when there is relative motion between the bodies. A body in motion experiences less friction as the surface irregularities are in contact for shorter periods of time. A body in motion tends to remain in motion due to inertia. Hence, sliding friction is less than static friction.

Additional information: Friction produces heat leading to loss of energy in various processes. It causes wear and tear of machine parts. It slows down motion as it is a retarding force. Even though it has many disadvantages, friction is extremely necessary in our daily life. It helps in motion by supplying traction. It enables us to hold objects. Vehicles are able to stop due to friction when brakes are applied. It is a necessary evil.

Note: It is a non-conservative force. Work done by friction is path dependent. It causes dissipation of kinetic energy in the form of thermal energy and hence total energy is not conserved. The different types of friction are static friction, sliding friction, rolling friction and fluid friction.