An air bubble doubles its radius on raising from the bottom of water reservoir to the surface of water in it. If the atmosphetic pressure is equal to 10 m of water, the height of water in the reservoir will be
A. 10 m
B. 20 m
C. 70 m
D. 80 m

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1 Answers

Correct Answer - C
`r_(2)=2r_(1)`
`(V_(2))/(V_(1))=((r_(2))/(r_(1)))^(3)=((2r)/(r))^(3)=8`
`V_(2)=8V_(1) `
`P_(1)V_(1)=P_(2)V_(2)`
`(P_(0)+h rho g)V_(1)=P_(2)xx8V_(1)`
`h rho g=80rhog-10rhog`
`therefore h=80-10` ltrgt `=70m.`

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