Question

A U-tube of cross section A and 2A as shown contains liquid of density d. Initially, the liquid in the two arms are held with a level difference h. After being released the levels equalize after some time. The work done by gravity forces on the liquid in the process is –

• A. $\frac{Adgh^{2}}{3}$
• B. $\frac{Adgh^{2}}{2}$
• C. $\frac{Adgh^{2}}{6}$
• D. $\frac{Adgh^{2}}{8}$

Answer 1

Answer: (A)

$\frac{Adgh^{2}}{3}$

Answer 2

DU = mg $\left( \frac{h}{2}–\frac{h}{6} \right)$ = mg $\frac{h}{3}$

= Adhg. $\frac{h}{3}$ = $\frac{Adh^{2}g}{3}$