# The acceleration of a bubble in water

• B

## Main Question or Discussion Point

Hi,

I have a question about a rising bubble.
I read that the initial acceleration of a bubble (with negligible mass) in water is 2g, where g is the gravitational acceleration. I understand that if a bubble rise then the water move around it, but I can't derive this equation.
Could someone help me out?

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BvU
Homework Helper
2019 Award
I see no reasonable argument for this statement.
What is your reference and what does it say to justify such a claim ?

ZapperZ
Staff Emeritus
This requires a clear reference to the source.

Zz.

hilbert2
Gold Member
Looking at the pdf file, the problem 52 seems to assume that the liquid has no viscosity, which isn't true in general.

BvU
Homework Helper
2019 Award
I did find a 2g here but don't see an explanation. And here it gets worse: 3.3 g ! But they do show how the 2g comes about in section 2 (of course ). So your derivation is available.

Must admit I learned to be a bit more open-minded: at first I didn't believe more than g is physically possible....

This one below ? I don't see it. But then again: you say the answer is 2. So: follow the steps and see where you end up