What name is given to the force that opposes motion between two surfaces in contact?

Friction is the force that opposes motion between two surfaces in contact. This resistance occurs when one surface attempts to slide over another. The amount of friction depends on various factors, including the nature of the surfaces in contact (e.g., rough vs. smooth) and the forces pressing them together.

Friction plays a critical role in everyday situations, allowing us to walk without slipping, cars to grip the road, and objects to stay still unless acted upon by an outside force. It acts in the opposite direction of the applied force, effectively countering the motion initiated by that force. Understanding friction is essential in physics because it affects the dynamics of moving objects and influences the design of everything from vehicles to sports equipment.