## 4.5 - Pressure

A force is a push or a pull. It is an interaction between two things. The way that the things touch is very important. That force applied over an area is called pressure. The relationship is normally stated as:

The greater the area to which the force is being applied, the less the pressure an object exerts. The smaller the area to which the force is being applied, the greater the pressure an object exerts.

Picture a brick that is 10 cm X 5 cm X 20 cm and weighs 10 N. No matter how you place the brick on a table it will have the same weight- the same force. The pressure the brick exerts on the table will be different, depending on what side it is lying.

If the brick is on its biggest side, 10 cm X 20 cm, the pressure will be the least. If it’s on the smallest side, 5 cm X 10 cm, the pressure is the greatest.

**P = F/A**The greater the area to which the force is being applied, the less the pressure an object exerts. The smaller the area to which the force is being applied, the greater the pressure an object exerts.

Picture a brick that is 10 cm X 5 cm X 20 cm and weighs 10 N. No matter how you place the brick on a table it will have the same weight- the same force. The pressure the brick exerts on the table will be different, depending on what side it is lying.

If the brick is on its biggest side, 10 cm X 20 cm, the pressure will be the least. If it’s on the smallest side, 5 cm X 10 cm, the pressure is the greatest.

When your bike tire has no air in it, there is very little pressure. This means that when you sit on the bike, a large area of the tire must be touching the ground to support your weight. If the tires have a lot of air pressure in them, a small part of the tire needs to touch the ground to support your weight.