If the work done in blowing a bubble of volume V is W, then the work done in blowing the bubble of volume 2V from the same soap solution will be
Correct Answer :
∛4 W
Solution :
To find the work done in blowing a soap bubble, we need to understand the relationship between the work done, the surface tension of the soap solution, and the surface area of the bubble.
A soap bubble has two free surfaces (an inner surface and an outer surface) in contact with air. Therefore, the work done in blowing a bubble of radius is equal to the surface tension multiplied by the total increase in surface area:
where is the surface area of a sphere of radius .
Substituting into the equation gives:
Now, let's relate the radius to the volume of the bubble. The volume of a spherical bubble is given by:
From this, we can express the radius in terms of the volume :
Taking the cube root on both sides:
Now, substitute this expression for back into the formula for the work done :
Since the surface tension of the same soap solution remains constant, we can see that the work done is directly proportional to :
Let be the work done to blow a bubble of volume .
Let be the work done to blow a bubble of volume .
Using the proportionality relation:
Substitute the values of and :
Therefore, the work done in blowing the bubble of volume 2V is .
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