1 Laws of friction

Laws of friction:

  1. The force of friction always acts in direction opposite to that in which body tends to move.
  2. Till the limiting value is reached, the magnitude of friction is exactly equal to the force which tends to move the body.
  3. The magnitude of the limiting friction bears a constant ratio to the normal reaction between the two surfaces of contact and this ratio is called coefficient of friction.
  4. The force of friction depends upon the roughness/smoothness of the surfaces.
  5. The force of friction independent of the area of contact between the two surfaces.
  6. After the body starts moving, the dynamic friction comes into play, the magnitude of which is less than that of limiting friction and it bears a constant ratio with normal forces. This ratio is called coefficient of dynamic friction.