Question

The frictional resistance for fluids in motion is

(a) proportional to the velocity in laminar flow and to the square of the velocity in turbulent flow

(b) proportional to the square of the velocity in laminar flow and to the velocity in turbulent flow

(c) proportional to the velocity in both laminar flow and turbulent flow

(d) proportional to the square of the velocity in both laminar flow and turbulent flow

This question was posed to me during a job interview.

This interesting question is from Loss of Energy in Pipes topic in section Flow Through Pipes of Fluid Mechanics

Answer 1

The correct choice is (a) proportional to the velocity in laminar flow and to the square of the velocity in turbulent flow

For explanation: According to the laws of fluid friction, rf / v (for steady streamline flow) and rf / v2(for turbulent flow), where rf is the frictional resistance and v is the velocity of flow.