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Two cylindrical vessels of equal cross-sectional area \mathrm{ 16 \mathrm{~cm}^{2}} contain water upto heights \mathrm{ 100 \mathrm{~cm}} and \mathrm{ 150 \mathrm{~cm}} respectively. The vessels are interconnected so that the water levels in them become equal. The work done by the force of gravity during the process, is  \mathrm{ [Take, density \: of \: water =10^{3} \mathrm{~kg} / \mathrm{m}^{3} \: and \: \mathrm{g}=10 \mathrm{~ms}^{-2} ] :}

Option: 1

\mathrm{0.25 \mathrm{~J}}


Option: 2

\mathrm{1 \mathrm{~J}}


Option: 3

\mathrm{8 \mathrm{~J}}


Option: 4

\mathrm{12 \mathrm{~J}}


Answers (1)

best_answer

The final water level is \mathrm{125 \mathrm{~cm}} Rise in the water Level of vessel 1 is \mathrm{25 \mathrm{~cm}} whereas there is corresponding fall in the water level of vessel 2 by \mathrm{25 \mathrm{~cm}}.

Work done by gravity is

\mathrm{W=-\Delta U}

      \mathrm{=U_{i}-U_{f}}

\mathrm{U_i =\left[\frac{\rho A h_1^2 g}{2}+\frac{\rho A_2^2 g}{2}\right] }

\mathrm{U_f =2\left[\frac{\rho A h^2 g}{2}\right] }

\mathrm{W =U_i-U_f }

      \mathrm{\left.=\frac{\rho A g}{2}[\left(h_1^2+h_2^2\right)-2 h^2\right] }

      \mathrm{=\frac{10^3 \times 16 \times 10^{-4} \times 10}{2}[1+2.25-2 \times 15625] }

\mathrm{ W =8[3.25-3.125] }

\mathrm{W =1 \mathrm{~J}}

Hence 2 is correct option.

Posted by

vishal kumar

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