Correct Answer - Option 2 : Equal to the external force
Explanation:
FRICTION
- The opposing force which comes into play when a body moves or tries to move the surface of another body is known as friction.
- The maximum value of the force of friction that comes into play before a body just begins to slide over the surface of another body is called limiting friction.
- The force of friction that comes into play between the surfaces of two bodies before the body actually starts moving is called static friction.
- The force of friction that opposes relative motion between two surfaces in contact is called kinetic or sliding friction.
- The frictional force developed, when a body rolls over a surface, is known as rolling friction.
- Static friction is a self-adjusting force and it adjusts itself so that it became equal to the applied force.
Advantages of Friction:
- Due to friction, we are able to move on the surface of the earth.
- The fibres of thread are held together due to the force of friction.
- The brakes applied in automobiles work only due to friction.
- Sledges are used in the Arctic region as friction is very low on the surface of the ice.
Disadvantages of Friction
- A lot of energy is wasted in the form of heat due to friction that causes wear and tear of the moving parts. • Due to friction, the speed of automobiles cannot be increased beyond a certain limit.
Methods of Reducing Friction
- By polishing, by lubrication, by proper selection of material, by using ball bearing, the friction can be reduced to some extent
