Question

If level of liquid starts decreasing slowly when the level of liquid is at a height $h_1$ above the cylinder, the block starts moving up. Then, value of $h_1$ is :

• A. $2h/3$
• B. $5h/4$
• C. $5h/3$
• D. $5h/2$

Answer 1

The correct option is C $5h/3$

The block would start rising once in equilibrium with the pressure from liquid above and the weight of the block balances the forces from bottom.

Under equilibrium,

$(P_0+\rho g{h}_1)\pi (2r{)}^2+\frac{\rho }{3}4\pi r^{2}hg=(P_0+\rho g(h_1+h_2)\left)\right(\pi (2r{)}^2-\pi (r{)}^2)$

Thus $h_1=\frac{5h}{3}$