question_answer

When a bore is made with a small drill in a hard board, the drill becomes very hot. But when the bore is made in a soft board, the drill does not become so hot. Why?

Answer:

                When a bore is made in a hard board, the friction between the drill and the board is quite large. A large amount of work has to be done in making the bore which produces a large amount of heat and the drill becomes too hot to touch. In case of the soft board, the friction is less, small work has to be done in making the bore. Hence heat produced is also small.