Pressure

DEFINITION:

“The force acting normally per unit area on the surface of a body is called ‘pressure’ ”.

OR

“Pressure is the amount of force applied per unit area of a surface. It is the force exerted perpendicular to the surface of an object in contact with another object or fluid”.

EXPLANATION:

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:

$Pressure = \Large \frac{Force}{Area}$

$\boxed{P= \frac{F}{A}}$

• Pressure is a scalar quantity. It’s S.I unit is $N/m^2$, which is also called $\text{Pascal (Pa)}$.

• Pressure is directly proportional to the force. Larger the force on body, greater will be the pressure.

• Pressure is inversely proportional to the area of surface. Smaller the area, greater will be the pressure.

EXAMPLES:

• The pressure exerted by the tip of pencil or that of the nail is large due to very small surface area.

• When came in contact with an object a fast moving bullet exerts huge pressure due to the small area of its tip and massive force.

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

• Ice skates have blades in the part that is in contact with ice. Therefore the skater's weight is concentrated on a small area and produce high pressure below the blades. This helps skater to skim over the ice.