Friction is a contact force that opposes the relative motion or the tendency of motion between two surfaces in contact. It arises due to microscopic irregularities present on the surfaces, which interlock when the bodies are in contact. In everyday life, friction plays a crucial role—walking, writing, and even holding objects are possible only because of friction.
In physics, friction is classified mainly into static friction and kinetic (sliding) friction. Static friction acts when there is no relative motion between surfaces and adjusts its magnitude to prevent motion up to a maximum value. Once this maximum is exceeded, motion starts and kinetic friction comes into play, which is generally smaller than limiting friction.
For IIT-JEE, understanding friction is important because it is often combined with concepts like Newton’s laws of motion, free body diagrams, inclined planes, and equilibrium. Careful analysis of direction, magnitude, and constraints of frictional forces is essential to solve numerical problems accurately.
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