A body is projected downward with velocity twice the terminal velocity from a very tall building. Find the velocity with which it will reach the ground.

When body is thrown with velocity greater than terminal velocity, the viscous force on the body is greater than the weight of the body. Therefore the body starts to retard and velocity of the body decreases. When the velocity of body decreases to terminal velocity, then net force on the body becomes zero and falls with constant velocity. Thus, the body reaches the ground with terminal velocity.