Fluid Mechanics Viscosity Question 133
Question: A soap bubble of radius R is blown. After heating the solution a second bubble of radius 2R is blown. The work required to blow the second bubble in comparison to that required for the first bubble is
Options:
A) Double
B)Slightly less than double
C)Slightly less than four times
D)Slightly more than four times
Show Answer
Answer:
Correct Answer: C
Solution:
[c] work done to form a bubble of radius R $ W_{1}=8\pi R^{2}T_{1} $ Work done to form a bubble of radius 2R $ W_{2}=8\pi {{(2R)}^{2}}T_{2}=32\pi R^{2}T_{2}\therefore \frac{W_{1}}{W_{2}}=\frac{T_{1}}{4T_{2}} $ If surface tension of soap solution is same, then $ W_{2}=4W_{1} $ But in the problem the temperature of solution is increased, so its surface tension decreases. $ \therefore W_{2}<4W_{1} $
BETA
