There are two identical small holes of area of cross-section a on the opposite sides of a tank containing a liquid of density ρ. The difference in height between the holes is h. Tank is resting on a smooth horizontal surface. Horizontal force which has to be applied on the tank to keep it in equilibrium is
The correct option is C. 2 ρ a gh.
Momentum of the mass of water coming out of the hole per sec is thrust.
Net thrust =F=FB−FA=dpBdt−dpAdt
=avBρ×vB−avAρ×vA
F=aρ(v2B−v2A)
F=aρ((√2ghB)2−(√2ghA)2)
F=2aρg(hB−hA)=2aρgh
∴ The horizontal force that has to be applied to the tank to keep it in equilibrium is F=2aρgh.