Properties Of Solids And Liquids Question 310
Question: The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is [MP PET 1991; MP PMT 1997]
Options:
A) $ 100dyne/cm $
B) $ 68.66dyne/cm $
C) $ 137dyne/cm $
D)$ 150dyne/cm $
Show Answer
Answer:
Correct Answer: B
Solution:
$ \Delta P=\frac{4T}{r}=hdg\Rightarrow T=\frac{rhdg}{4} $
$ =\frac{0.35\times 0.8\times 1\times 10^{3}}{4} $
$ =70\ dyne/cm $
$ \equiv 68.66\ dyne/cm $
