Define pressure and its si unit and formula

The word pressure gives a mental image of something being pressed.

Pressure is defined as force per unit area. The SI unit of pressure is the pascal (Pa), which is newton(N) per square meter (m2).

Pressure in (Pa) = Force (in N)/ Area ( in m2)

Some very important and useful devices such as the syringe, dropper, and drinking straw, work on the principle of pressure.


Pressure depends on two main factors: force and surface area.

  1. Increasing the force on an area increases the pressure produced.
  2. Similarly, Increasing the area over which a particular force acts decreases the pressure produced.

Fluid Pressure

Liquid and gases are together called fluids. Fluids exert pressure on all bodies immersed in them and all the walls of the containers that hold them. If you try to push an inflated balloon into a bucket of water, you will find that as you try to push down the balloon, the water seems to be pushing it back upward! In fact, if you stop pushing the balloon, the balloon will be pushed back to the surface.

Calculate the pressure if a force of 10 N is applied on an area of 10 mm square.

Here, the area is not in meter Square. To change it into a meter square, we divide the area by 1, 000000.


Area = 10/1, 000000 =0.000010 metre square


Pressure = Force /Area = 10 N/0.000010 metre square =1, 1000000 pa

Pressure depends on both force and area.

If a person sleeps on the bed of iron nails then it will be less affected but if a person sleeps on a single iron nail then the person will be more affected.

A knife has a sharp edge, due to the less area it exerts more pressure on the object. So it can cut any object easily.

If any weapon has less on its edge, it means it will exert more pressure when it is used in cutting the object.