Can you stand on a single leg easily that you can do by using your two legs? The shoes pierce into the mud when one walks on soft mud wearing a high hill. But if one does so wearing a flat pair of shoes, then it does not get into the mud. We will see that it happens due to the change of pressure.
The force exerted perpendicularly to unit are of a body is called pressure. Let a force F act perpendicularly on area A of a surface, then pressure, P = F/A
i.e. Pressure = Force / Area
It is noted that less the area A, more is the pressure P and more the force F. more is the pressure P.
(i)The area of the sharp edge of a nail is very small. So when the sharp end of the nail is placed on a wood like surface and hammered on the flat head of the nail, comparatively more pressure is exerted on the sharp end as a result the nail easily enters into the substance.
(ii)The area of the sharp edge of the knife is very small. So, by placing the sharp edge of the knife on a substance if force is applied, then more pressure acts on the substance along edge. Therefore the substance can easily be cut.
More pressure is felt on the sharper edge of the pin when force is applied on its flat end. When force is applied on the flat end of the blunt pin, less pressure is exerted on the bhmt end So, it is easy to hole a paper by a sharper pin.
Unit of pressure:
If we divide the unit of force by the unit of area, we get the unit of pressure. Therefore the unit of pressure is Nm-2. It is called pascal (Pa).
1 Pa = 1 Nm-2
If a force of 1 N force is applied perpendicularly to an area of lin2 then the pressure generated is known as 1 Pa.