The two major forces opposing the motion of a vehicle moving on a level road are the rolling resistance of the tires, F and the aerodynamic drag force of the air flowing around the vehicle, Fd, given respectively by Fr fW, Fd= Cd A½ ρV2. Where f and Cd are constants known as the rolling resistance coefficient and drag coefficient, respectively, W and A are the vehicle weight and projected frontal area, respectively, V is the vehicle velocity, and ρ is the air density. For a passenger car with W= 3550 lbf, A= 23.3ft2, and Cd= 0.34, and where f=0.02 and ρ= 0.08 lb/ft3.
(a) Determine the power required, in hp, to overcome rolling resistance and aerodynamic drag when V is 55 mi/h.
(b) Plot versus vehicle velocity ranging from 0 to 75 mi/h (i) the power to overcome rolling resistance, (ii) the power to overcome aerodynamic drag and (iii) the total power, all in hp, what implication for vehicle fuel economy can be deduced from the results of part (b)?