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. $0.06gm$
• B. $0.6gm$
• C. $6gm$
• D. $60gm$

Answer 1

The correct option is B $0.6gm$

$T=3\times {10}^{-2}N/m$

Effective length$=2l=20cm$ because both surfaces are open

$F=TL=3\times {10}^{-2}\times 20\times {10}^{-2}=6\times {10}^{-3}6\times {10}^{-3}=m\times 10m=6\times {10}^{-4}kgm=0.6gm$