Friction:
Friction is defined as the resistance to motion of one item relative to another. It may take many different shapes.
Advantages of Friction:
To run different machine efficiently, frictional force between the movable parts should be minimized. But it is wrong to think that machines would have been more efficient if friction was absent.
1. Human beings and animals can walk on the ground. A force is exerted obliquely. While walking, the reaction force generated due to friction makes it possible for a man to move forward without slipping.
2. Trees can hold the ground tightly with their roots. Otherwise, plants could have been uprooted easily.
3. Striking can be held with the fingers and palms of our hands.
4. Ladders can be supported on vertical walls.
Disadvantages of Friction:
1. Friction always resists motion, so extra energy is required to overcome it.
2. It causes wear and tear on machines.
3. Friction decreases the life expectancy of moving parts of vehicles.