Question

A liquid film is formed over a frame ABCD as shown in figure. Wire CD can slide without friction. The mass to be hung from CD to keep it in equilibrium is

• A. $\frac{Tl}{g}$
• B. $\frac{2Tl}{g}$
• C. $\frac{g}{2Tl}$
• D. T × l

Answer 1

Answer: (B)

$\frac{2Tl}{g}$

Answer 2

Weight of the body hung from wire (mg) = upward force due to surface tension (2Tl ) ⇒ $m = \frac{2Tl}{g}$

$v = \sqrt{\frac{6T}{d}\left( \frac{1}{r} - \frac{1}{R} \right)}$