Question

A small ball of mass m and density ρ is dropped in a viscous liquid having densityρo. After some time, ball falls with a constant velocity. Calculate viscous force acting on the ball.

Answer 1

Volume of the ball, v = m/ρ; mass of liquid displaced by the ball.

ρ = density of ball

When the ball falls with a constant velocity

⇒ viscous force = effective weight of the ball 

or F = mg = m’g = (m – m’)g