Radius of soap bubble

Classical Mechanics Level 2

Two soap bubbles of equal radii 8 cm are stuck together with an intermediate film separating them. The surface tension of solution forming bubbles is 7 × 1 0 3 N/m 7\times 10^3 \text{ N/m} . What will be the distance between the central of soap bubbles (in cm)?


The answer is 8.

Mohit Swain by Mohit Swain , 21, India

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1 solution

Pranav Shankr
Apr 24, 2020

Use Lami's theorem at the interface

0 Helpful 0 Interesting 0 Brilliant 20 Confused

Common interface Radius of two joining soap bubbles is given by R=r1*r2/|r1 - r2|. Here, r1 is equal to r2 which is further equal to 8 cm. So, on putting the value in the equation, we get the value of radius as infinite (which is not possible). So, the radius of common interface will not exist. IF it still exists, then its radius will be very small (which will be negligible) and it will exists symmetrically between the bubbles. Therefore, the distance between the centers is given as radius of one soap bubble+radius of common interface (which is negligible here). Hence, distance between the centers = 8cm

Arghyadip Sengupta - 10 months, 3 weeks ago

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