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Please explain pressures of which two points are equated....

Please explain pressures of which two points are equated....

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Grade:12

2 Answers

Vikas TU
14149 Points
4 years ago
Dear student 
The lower point pressure and the pressure at distance r will be equated, 
Good Luck ….............................................
Arun
25750 Points
4 years ago

The air bubble is in the shape of a sphere.

Now, the volume of an air bubble (V) with radius (r) is given by,

\begin{align} V = \frac{4}{3}\pi r^3 \end{align}

The rate of change of volume (V) with respect to time (t) is given by,

\begin{align} \frac{dV}{dt} = \frac{4}{3}\pi \frac{d}{dr}(r^3).\frac{dr}{dt} \;\;\;[By\; Chain\; Rule] \end{align}

\begin{align} = \frac{4}{3}\pi (3r^2).\frac{dr}{dt} \end{align}

\begin{align} = \frac{4}{3}\pi r^2.\frac{dr}{dt} \end{align}

It is given that

\begin{align} \frac{dr}{dt}=\frac{1}{2} cm/s .\end{align}

Therefore, when r = 1 cm,

\begin{align} \frac{dV}{dt}=4\pi(1)^2.(\frac{1}{2})=2\pi\; cm^3/s \end{align}

Hence, the rate at which the volume of the bubble increases is 2π cm3/s.

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