Question

In which of the following case is friction useful?

• A. Heating of an electric fan.
• B. Production of noise in machines.
• C. Wear and tear of shoes.
• D. Use of a chalk for writing.

Answer 1

The correct option is D

Use of a chalk for writing.

Friction is called a necessary evil as it has many positive effects apart from a few drawbacks. For example, it is because of friction that we are able to hold a chalk and write with it. The chalk sticks on writing board because of friction. On the other hand, heating and wear and tear of equipments, production of noise etc. are undesirable effects of friction.