Question

State a device that utilises ‘Pascal’s law’ and also explain how it works.

Answer 1

Hint : Pascal’s law states that if a force is applied on a confined, uniform fluid, the pressure generated in the fluid by this force is equally transmitted in all directions. And this pressure acts at right angles to the walls that enclose the fluid.

Complete step by step answer
The concept of pressure as well as Pascal’s law was given by Blaise Pascal. Pressure is defined as the force acting per unit area, it can be represented as-
 $\Rightarrow P = \dfrac{F}{A} $
Where $ P $ is the pressure, $ F $ is the force acting on a surface, $ A $ is the surface area where the force acts.
A device that utilises Pascal’s law is hydraulic lift. It is used to lift heavy objects like cars or other heavy vehicles.
In a hydraulic lift, there are two platforms, one has a large surface area while the other platform has a smaller area.
The platform with a smaller area is a small cylinder and force is applied into it.
The platform with the larger area is the platform which lifts upwards.
Both platforms are joined by a closed path, and the inside of this arrangement is filled with a fluid, preferably water or oil.
Let the force applied at the smaller platform be $ {F_1} $ and the force which acts on the larger platform be $ {F_2} $ .
Let the area of the smaller platform be $ {A_1} $ and the area of the larger platform be $ {A_2} $ .
Then according to Pascal’s law, the pressure across the fluid will be the same, which means that the pressure at the smaller platform is equal to the pressure at the larger platform.
 $\Rightarrow {P_1} = {P_2} $
 $\Rightarrow \dfrac{{{F_1}}}{{{A_1}}} = \dfrac{{{F_2}}}{{{A_2}}} $
 $\Rightarrow {F_1}{A_2} = {F_2}{A_1} $
Thus, Force on the smaller platform is given by,
 $\Rightarrow {F_1} = {F_2}\dfrac{{{A_1}}}{{{A_2}}} $
We know that $ {A_1} < {A_2} $ thus, the ratio $ \dfrac{{{A_1}}}{{{A_2}}} < 1 $ .
This makes $ {F_2} > {F_1} $ .
Therefore the force with which the object is lifted is greater than the force which is applied by the compressor. This results in a net upward motion of the platform with a larger area.

Note
Pascal’s law is valid only in a confined, uniform, and incompressible fluid. A confined space means that space, where the fluid is filled, is a closed system, nothing can enter or exit it. A uniform fluid means a fluid of the same composition throughout the body. And incompressible means that the volume of the fluid remains constant.