Q.

A small spherical ball of radius r, falling through a viscous medium of negligible density has terminal velocity 'v'. Another ball of the same mass but of radius 2r, falling through the same viscous medium will have terminal velocity                                  [2024]

1 v/2  
2 v/4  
3 4v  
4 2v  

Ans.

(1)   

       Since density is negligible hence Buoyancy force will be negligible

        At terminal velocity,

        Mg=6πηrv

       v1r (as mass is constant)

        Now, vv'=r'r

        r'=2r

       So, v'=v2