Question

A soap film of surface tension $3\times {10}^{-2}N{m}^{-1}$ formed in rectangular frame, can support a straw. The length of the film is $10cm$. Mass of the straw the film can support is

• A. $0.06g$
• B. $0.6g$
• C. $6g$
• D. $60g$

Answer 1

The correct option is B $0.6g$

Force applied by the surface tension by the tiles$=2Tl$

Weight of the straw$=Mg$

To maintain equilibrium,

$2Tl=Mg$

$\Rightarrow 2\times (3\times {10}^{-2})\times \left(0.1\right)=M\left(10\right)$

$\Rightarrow 6\times {10}^{-4}kg=M$

$\Rightarrow 0.6g=M$

The mass of straw is $0.6g$

option B is correct.