Question

State and explain the laws of limit friction

Answer 1

- Hint: In equilibrium , limiting force of friction between two conducting surfaces is equal and opposite to the applied force .so, when a force applied on the body t rest , to put it in motion at that time the minimum force is required to make the body slide or move , is called limiting friction.

Complete step-by-step solution -

The moment, this limiting friction is that value of force beyond which , if the force is applied further, the body will no longer remain in rest and it will start moving.
Laws of limiting friction
1) The force of limiting friction depends upon the nature of the surface in contact and acts tangentially to the interface between the two surfaces.
2) The force of limiting friction between two surfaces in contact is independent of the area of contact.
3) Limiting friction is directly proportional to the magnitude of normal reaction N between two surfaces in contact.
F∝N
F= µN
where µ is the constant of proportionality and known as coefficient of friction.

4) The direction of force of friction is always opposite to the direction in which the body moves or tends to move.
5) Limiting friction acts tangential to the two surfaces in contact.

Note: Generally friction acts on a body to restrict its movement. When force applied increases, the body tends to move. The friction that is present at that point of the time is known as limiting friction.