# Thrust and Pressure

Pressure is the force acting on a unit area of the object. The effect of force depends on the area of the object on which it acts.
The pressure depends on two factors:

1. Force Applied
2. Area over which force acts.

The same force can produce different pressures depending on the area over which it acts, if a force acts over a large area of an object, it produces a small pressurem but if the same acts over a small area of the object, it produces a large pressure.

## Defination of Pressure

Presure is the force acting perpendicularly on a unit area of the object.
Pressure = Force / Area

## Thrust

The force acting on a body pependicularly to its surface is called thrust. Thrust is the total force acting on the surface of body. The SI unit of thrust is newton(N).

## Archimedes' Principle

Archimedes' principle states that when an object is wholly or partially immersed in a liquid, it experiences a buoyent force which is equal to the weight of liquid displaced by the object.

Boyant Force acting on a body = Weight of liquid displaced be that object.
The magnitude of boyant force is equal to the weight of liquid displaced by immersed object

## Boyent Force

When an object is immersed in a liquid, it experiences an upward force. This upward force is called 'buoyant force' or 'upthrust' and the tendancy of liquid to apply an upward force on an object placed in it is called as Buoyancy

## Factors Affecting Boyant Force

Their are two main factors affecting boyant forces:

1. The buoyant force exerted by a liquid depends on the volume of the solid object immersed in the liquid.

2. The buoyant force exerted by a liquid depends on the density of the liquid in which the object is immersed. As the density of liquid increases the buoyant force exerted by it also increases.

## Density

Some substances appear to be heavy whereas others are light. The density of a substance is defined as mass of the substance per unit volume
Density = Mass of the substance / Volume of the substance. The SI unit of density is 'kilogram per cubic metre'.