# Force of bubble

1. Feb 11, 2016

### werson tan

1. The problem statement, all variables and given/known data
why the force of bubble is given by the formula of 2(2 pi R ) σs ? why not (2 pi R ) σs + (2 pi R+ ΔR) σs ? Since the radius of th outer circumfernece and inner circumference are the different ?

2. Relevant equations

3. The attempt at a solution

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2. Feb 11, 2016

### haruspex

Because for most purposes the difference is too small to worry about. The thickness of the bubble wall is usually far smaller than the radius of the bubble.

3. Feb 17, 2016

### werson tan

i have one more question here . I was also told that the pressure at the concave side of the bubbles is higher ... why is it so ? is it because of the circumference of the pressure at the concave side is higher?