Question

When a capillary tube of radius 'r' is immersed in water, rise of water is upto height 'h'. The mass of water in capillary tube is 'm'. When another capillary tube of radius 'xr' is immersed in water, the mass of water that will rise in this tube is

• A. \(x\cdot m\)
• B. \(\frac{m}{x}\)
• C. \(x^2m\)
• D. \((x+1)m\)

Hint:

A soap film has two free surfaces, so the force is 2 T times the length of the boundary.

Answer 1

The Correct Option is A

Step 1: Surface energy approach:
Take the force on one side of length $L$: each surface exerts $TL$, so both surfaces together give $2TL$.

Step 2: All four sides:
A square frame has 4 sides, so the total is $4\times2TL = 8TL$ (B).

Final Answer:
$8TL$. \[ \boxed{8TL} \]