As we explained in earlier chapters, the drag force acting on a car is determined experi...

As we explained in earlier chapters, the drag force acting on a car is determined experimentally by placing the car in a wind tunnel. The drag force acting on the car is determined from

where

F_d = measured drag force (N or lb)

C_d = drag coefficient (unitless)

ρ = air density (kg /m3 or slugs /ft³)

V = air speed inside the wind tunnel (m/s or ft /s)

A = frontal area of the car (m² or ft²)

The power requirement to overcome the air resistance is computed by

Plot the power requirement (in hp) to overcome the air resistance for a car with a frontal area of 2800 in², a drag coefficient of 0.4, and for an air density of 0.00238 slugs/ft³. Vary the speed from zero to 110 ft /s (75 mph). Also, plot the rate of change of power requirement as a function of speed.