When a sphere falling in a viscous fluid attains a terminal velocity, then

Options

A. viscous force plus buoyant force becomes equal to force of gravity
B. viscous force is zero
C. viscous force plus force of gravity becomes equal to buoyant force
D. buoyant force becomes equal to force of gravity

Answer

A

Explanation

When a sphere falls through a viscous medium it accelerates initially due to gravity. As a result of this its velocity increases, hence viscous force also increases. Finally when viscous force plus buoyant force becomes equal to the force of gravity, the net force becomes zero and so does the acceleration. Then the sphere descends with a constant velocity. This constant velocity is called terminal velocity.