Question

A cylindrical opening in the cover of a vessel (A) filled with water is tightly closed by a piston
(B) of mass 20 kg and radius 10 cm. A vertical tube (C) of radius 5 cm is attached to the piston
Assuming that the piston is in equilibrium in contact with water surface, the height of water
column in the tube (C) above the level of the piston is nearly
1) 85 cm
2) 105 cm
3) 54 cm
4) 38 cm

Answer 1

Answer:

All are in equilibrium

Piston is applying a force equal to mg = 200 N

So pressure = F/A

=

$= \frac{200}{\pi {0.1}^{2} } = \frac{2}{\pi} \times {10}^{4} \: n{m}^{ - 2}$

Pressure at height h is pgh are equal

$\rho \: gh = \frac{2}{\pi} \times {10}^{ 4} \\ {10}^{3} \times 10 \times h = \frac{2}{\pi} \times {10}^{ - 4} \\ \\ h = \frac{2}{\pi} \: m = \frac{200 \times 7}{22} cm \approx63.67 \: \: cm$

**A diagram will help to understand question more .