Question

Why it is difficult to fix a nail on a wall

Answer 1

When you force the nail into the wall by striking with hammer it displaces the wall material to pass through. This wall material like brick or wood try to achieve the initial state due to elasticity and gets firlmy attached to the nail with much force. Since the force on nail is large, the friction becomes large due to which it becomes difficult to remove the nail out of the wall again.

Answer 2

It is not difficult but easy to fix the nail on the wall as the surface area of the pin is less so the pressure apllied on the wall be more so the pin will go in easily while an object with a very large surface area will not