Question

In which of the following cases, friction is a friend?

• A. Heating of a working mixer
• B. Noisy machines
• C. Wearing of machines
• D. Using pen for writing

Answer 1

The correct option is D

Using pen for writing

Friction is called a necessary evil as it has many positive effects. For example, it is because of friction that we are able to walk and write.
While writing, the ball inside the pen rolls because of the frictional force acting between the ball and the surface of paper. This causes the ink to fall out on the paper. Otherwise, the ball slides if frictional force is absent.