Friction
It has been observed that the surfaces of the bodies are never smooth. When a body having smooth surface is moved over the surface of another smooth body then certain interlocking will take place. This interlocking is due to the roughness and irregularities on both the surfaces. A force will act in an opposite direction of motion of upper body which is known as friction or force of friction. The friction arises due to the relative motion between two parts of a machine. Some energy gets wasted in overcoming the friction.
Types of friction:
Static friction: The friction experienced by a body, when at rest is known as static friction.
Dynamic friction: The friction experienced by the body, when in motion is called dynamic friction. The dynamic friction can be classified as.
a. Sliding friction: The friction experienced by a body, when it slides over the surface of another body is called sliding friction.
b. Rolling friction: The friction experienced by the surfaces which has balls or rollers placed between them.