Question #7dd19

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Answer 1 · 2017-05-29T02:28:23

To choose the correct option we are to analyse the forces acting on the bubble .

Let the volume of the bubble at the certain instant be $V$ .

The mass of the gaseous material in the bubble be $m$ .

The downward gravitational pull on it will be $Fdarr=mg=Vdg$ , where $d=$ density of the gaseous material of the bubble.

The upward buoyant force on it at the inatant considered will be $Fuarr=Vrhog$ , where $rho=$ density of boiling water.

We know that $rho >d$

Hence $Fuarr>Fdarr$

So net force acting at that instant $F_N=Fuarr-Fdarr>0$

Hence the positive acceleration of the bubble at that instant will be $a=F_N/(Vd)=(rho-d)/d$

So option (a) is correct.