Critical Velocity and Reynolds Number

Two stones with radii 1:2 fall from a great height through the atmosphere. Their terminal velocities are in the ratio ______ 

What is the net weight of a body when it falls with terminal velocity through a viscous medium?

A square metal plate of area 100 cm² moves parallel to another plate with a velocity of 10 cm/s, both plates immersed in water. If the viscous force is 200 dyne and the viscosity of water is 0.01 poise, what is the distance between them?   

The relative velocity between two parallel layers of water is 8 cm/s and the perpendicular distance between them is 0.1 cm. Calculate the velocity gradient. 

A raindrop of radius 0.3 mm falls through the air with a terminal velocity of 1 m/s. The viscosity of air is 18 x 10^-6 N-s /m². Find the viscous force on the raindrop.  

State the formula for critical velocity in terms of Reynold's number for a flow of a fluid.

A horizontal force of 1 N is required to move a metal plate of area 10^-2 m² with a velocity of 2 × 10^-2 m/s, when it rests on a layer of oil 1.5 × 10^-3 m thick. Find the coefficient of viscosity of oil.

Multiple Choice Question.

Two hailstones with radii in the ratio of 1:4 fall from a great height through the atmosphere. Then the ratio of their terminal velocities is