Lecture 25: Friction between solid and fluid - drag force

This is the 25th lecture of the NPTEL course “Newtonian Mechanics with Examples” by Shiladitya Sengupta, Dept. of Physics, IIT Roorkee. In this lecture we critically examine the drag force which is present when a solid object moves through a fluid. We derive its velocity dependence, introduce drag coefficient, Reynold’s number and viscosity. We also derive the velocity dependence of the drag force at high and low Reynolds number regimes from physics principles.