# The velocity of small ball of mass M and density d1 when dropped a container filled with glycerine…

Q: The velocity of small ball of mass M and density d1 when dropped a container filled with glycerine becomes constant after some time. If the density glycerine is d2, the viscous force acting on ball is

(a) $\displaystyle \frac{M g d_1}{d_2}$

(b) $\displaystyle M g(1-\frac{ d_2}{d_1})$

(c) $\displaystyle \frac{M( d_1 – d_2 )}{g}$

(d) $\displaystyle \frac{M d_1}{d_2}$

Ans: (b)

Sol:

Viscous force = Weight – Buoyancy

= V d1 g – V d2g

= V d1g(1-d2/d1)

= M g (1 – d2/d1)