What is friction? - Leaving Cert Physics - Question (c) - 2006

Friction is a force that opposes motion between two surfaces in contact. It acts parallel to the interface of the surfaces and is essential in everyday activities, such as walking or driving, where it allows for motion control.

Friction arises due to the microscopic roughness of surfaces which interlock, creating resistance against the moving object. There are two main types of friction:

1. Static Friction: The force that prevents two surfaces from starting to move against each other.
2. Kinetic Friction: The force that opposes the movement of two surfaces sliding past each other.

Understanding friction is crucial in many fields of physics and engineering, as it influences the design of machines, vehicles, and many mechanical systems.