Question

A small ball of lead is falling freely in viscous liquid. The velocity of the ball

• A. goes on increasing
• B. goes on decreasing
• C. remains uniform all along
• D. increases to a certain value and subsequently the ball continues to fall with this velocity.

Answer 1

The correct option is D increases to a certain value and subsequently the ball continues to fall with this velocity.

At first the velocity of ball will increase because of dominating weight, but as it gains velocity an opposing force will start acting on it.

$F=6\pi \eta rv$

At certain velocity the weight will get balanced by buoyancy and viscous force. The speed of the body will stop increasing further that velocity is called terminal velocity.