CBSE Class 11-science Answered

To solve this problem we need to use Pascal's law.

The  mass to be lifted = m = 80 kg

Force Required to lift up = F = mg

= 80 x 9.8 

=784  N

Let  Radius of the larger piston = R₁ 

     Radius of the smaller piston = R₂

Given that,

R₁ = 5 R2

Area of larger piston = A₁ = π R₁²

Area of smaller piston = A₂ = π R₂²

A₁ = 25 A₂

Pressure = F/A

According to pascal's law,

Pressure applied will be the same

P₁ = P₂

F₁/A₁ = F₂/A₂  

F₁/25A₂ = F₂/A₂  

F₁/25 = F₂  = 784 N

Area of larger piston is larger therefore water will exert more force on the larger piston.

Since area of larger piston is 25 times larger,  therefore minimum force we need to apply on the smaller piston is 1/25 times the force required,

minimum force required= 1/25 x 784

       = 31.36 N

 Answer =31.36 N