Force and Pressure

Pressure

• Force acting per unit area is known as pressure.
• $\begin{array}{l}�=\frac{�����}{����}\end{array}$
• SI unit is Pascal.

Distribution of pressure

• Force acting on a smaller area applies more pressure than the same force acting on a larger area.
• Examples: Porters place a round cloth on their heads to increase surface area and reduce pressure.
• A sharp knife cuts better as more pressure is exerted over a smaller area.

Pressure in fluids

The pressure exerted by a fluid(gases or liquids) in a container is transmitted undiminished in all direction on the walls of the container.

Upthrust

The upward force exerted by a fluid on an object is known as upthrust or buoyant force.

Atmospheric Pressure

Gaseous pressure

Gases exert the same pressure on the walls of the container in all directions.

Atmospheric pressure

• Our atmosphere extends to several kilometres above sea level. The weight of the air acts as pressure known as atmospheric pressure.
• The pressure in our body balances the atmospheric pressure and that is why we do not feel it.