Question

Two cylindrical vessels fitted with pistons A and B of area of cross-section 8 cm² and 320 cm² respectively are joined at their bottom by a tube and they are completely filled with water. When a mass of 4 kg is placed on piston A, Find:

1. the pressure on piston A,
2. the pressure on piston B, and
3. the thrust on piston B.

Answer 1

Given that the force applied to the smaller piston A is 4 kg

Area of cross-section of piston A = 8 cm²

Area of cross-section of piston B = 320 cm²

(i) Pressure acting on piston A in the downward direction = `"Thrust"/"Area"`

= `(4  "kg")/(8  "cm"^2)`

∴ Pressure acting on piston A = 0.5 kg cm^-2

(ii) According to Pascal's Law

Pressure acting on piston B = Pressure acting on Piston A = 0.5 kg cm^-2

(iii) Thrust acting on piston B in the upward direction

= Pressure × Area of B

= 4 kg × `(320  "cm"^2)/(8  "cm"^2)`

∴ Thrust acting on piston B in the upward direction = 160 kgf.