Question

An athlete is running a 400m race around a 400m track. On the backstretch the athlete's velocity is 8m/s but he is running into a 2m/s headwind. How large is the drag force that acts on him? Assume that the density of the air is 1.2kg/m^3, his cross sectional area is 0.5m^2, and the coefficient of drag is 1.1.

Answer 1

Answer:

33 N

Explanation:

v = Velocity of fluid = 8+2 = 10 m/s

$\rho$ = Density of fluid = 1.2 kg/m³

C = Coefficient of drag = 1.1

A = Cross sectional area = 0.5 m²

Drag force is given by

$F=\frac{1}{2}\rho CAv^2\\\Rightarrow F=\frac{1}{2}\times 1.2\times 1.1\times 0.5\times (8+2)^2\\\Rightarrow F=33\ N$

The drag force on the athlete is 33 N