# Question #7dd19

##### 1 Answer

May 29, 2017

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

The mass of the gaseous material in the bubble be

The downward gravitational pull on it will be

The upward buoyant force on it at the inatant considered will be

We know that

Hence

So net force acting at that instant

Hence the positive acceleration of the bubble at that instant will be

So option (a) is correct.