Friction, a force that opposes motion, exists in two primary forms: static and sliding. Static friction is the force that prevents an object from starting to move, while sliding friction acts on an object already in motion. The key difference lies in the nature of the surface interactions.
When an object is stationary, the microscopic irregularities on its surface have ample time to interlock with those of the surface it’s resting on. This interlocking creates a stronger resistance to any applied force, resulting in higher static friction. In contrast, when an object is sliding, the contact points between the surfaces change rapidly. This reduced contact time limits the degree of interlocking, leading to lower sliding friction.
Consequently, it generally requires more force to initiate motion (overcoming static friction) than to maintain that motion (counteracting sliding friction). This principle is evident in everyday experiences, such as pushing a heavy box across a floor or sliding a book on a table. The initial push demands greater effort due to static friction, while subsequent movement is smoother as sliding friction takes over.
