Question

why friction is called friend and evil​

Answer 1

Friction is a necessary evil acting both as a friend and a foe. Examples of friction as a friend: We are able to walk because of frictional forces between ground and our feet. ... nails and screws stick to the wall surfaces because of friction

Answer 2

Friction is called necessary evil -

Frictional force causes a lot of losses in general upkeep and wear and tear of machinery. Hence it is considered as a evil. But almost all crucial tasks cannot be carried out without the presence of friction. Hence it is considered as a necessary evil .

Friction is called friend -

(i) Friction allows us to grip and catch different objects.

(ii) It helps us to walk comfortably on the surface.

(iii) It helps to minimize the speed or to stop the moving objects. .