Question

Question #7dd19

Answer 1

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.