A pizza delivery company considers installing a thin, smooth, square sign with a side length of 0.50 m on the roofs of the delivery cars. Consider that the typical car moves with an average speed of 40 km/h over an average distance of 5 km per delivery.
a) Calculate the additional energy that would be consumed (compared to a car without a sign) for the average delivery, if the sign is i) normal and ii) parallel to the direction of motion.
b) If the specific fuel consumption is roughly 0.6×10^-6 kg/J, the specific gravity of the fuel is roughly equal to 1, the efficiency of the engine etc. is also taken as 1 and the price of the fuel is 0.70 $/liter, calculate the additional cost per delivery, because of the sign, for cases i) and ii). What would you do, concerning the sign, if you were the pizzeria manager? If you decided to keep it, would you have to increase the delivery charge?

Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.