Question

why is it easy to drive a nail through it sharp edge into a wooden block

Answer 1

because it's sharp edge has small area and small area leads to great pressure as per formula:

pressure= force/area

Answer 2

We know that,

Pressure is inversely proportional to Area of contact.

or, Pressure=Force/Area

Thus, a nail having small area of contact can apply more pressure, and is easily driven into the wooden block.

Hope it helps.