Question

Drag force is directly proportional to ________

(a) Density of fluid

(b) Mass density

(c) Area

(d) Flow speed

I got this question in an interview.

This is a very interesting question from Drag on a Sphere topic in section Boundary Layer Flow & Forces on Sub-merged Bodies of Fluid Mechanics

Answer 1

The correct answer is (a) Density of fluid

The best explanation: Drag force is directly proportional to density of the fluid. It is the force that acts opposite to the relative motion of any object moving with respect to its surroundings. Thus, the correct option is ‘a’.