Question

A cylindrical tank, filled with water, has an area of 10m^2. A piston covers its entire top surface. A uniformly distributed load of 1000N is applied on the piston from top. A hole of area 0.001m^2is at the bottom of the tank. Find the speed of efflux when the height of water level is 0.1m .

(a) 24.5m/s

(b) 1.48m/s

(c) 0.2m/s

(d) 2m/s

I got this question during an online interview.

The origin of the question is Fluids Mechanical Properties topic in section Mechanical Properties of Fluids of Physics – Class 11

Answer 1

Right choice is (b) 1.48m/s

The explanation: We should apply Bernoulli theorem between the top surface of water and the hole.                     The area of hole is very small when compared to the area of the tank.                                                                           So, 1/2ρv^2 at the top surface of the tank can be neglected.

P0 + F/AP + ρgh = P0 + 1/2ρv^2

∴ 1000/10 + 1000*10*0.1 = 0.5*1000 *v^2

∴ v = 1.48m/s