Pressure types _bookeragency

 Pressure

Press a pencil from its ends between the palms.

⦁ The palm pressing the tip feels much more pain than the palm pressing its blunt end. We can push a drawing pin into a wooden board by pressing it by our thumb .It is because the force we apply on the drawing pin is confined just at a very small area under its sharp tip.

⦁ A drawing pin with a blunt tip would be very difficult to push into the board due to the large area of its tip.

In these examples,

 we find that the effectiveness of a small force is increased if the effective area of the

force is reduced. The area of the tip of pencil or that of the nail is very small and hence increases the effectiveness of the force.

 The quantity that depends upon the force and increases with decrease in the area on which force is acting is called pressure. 

"The force acting normally per unit area on the

surface of a body is called pressure".

How to calculate pressure

If F is the magnitude of a force exerted perpendicular to a given surface of area A, then the pressure P equals to the force divided by the area:

As the force is measured in newtons (N) and area 

in square meters (m ). Therefore in SI system unit of pressure is newton per square meter (Nm ). It is also known as Pascal (Pa)

High pressure, low pressure

The pressure under the studs on the soles of football shoes is high enough to sink into the ground, which gives extra grip.

 Ice skates have blades in the part that is in contact with ice. Therefore the skater's eight is concentrated on a small area. The effect of this high pressure s ice just below the blades. 

This gives

⦁ the thin film of water, which provide lubrication for the Kate to skim over the ice. As the skate moves on, the alter re-freezes. On very cold days, the pressure may to be enough to melt the ice, and skating is impossible.

⦁ An elephant has broad soles to reduce the pressure exerted on the ground.

⦁ Wide shoulder pads of school bg reduce pressure on the student's shoulder