QUESTION 1 a) Calculate the drag force of an express bus of 12-meter in length, 2.6-meter-wide and 3- meter in height moving at a constant speed of 90 km/h along a straight highway in a calm windless night. A small geometrically similiar model of the bus with a frontal area of 0.078 m2 was tested in a wind tunnel at 15 m/s and the drag force acting on the model in the flow direction was measured to be 7.161 N. [CO1/P01/C2] (10 marks) b) Using the information in part (a), now calculate the drag force of the same express bus assuming that the express bus is a rectangular box having a smooth surface on all sides and calculate only the surfaces that are parallel to the air flow. Then find the location where the air flow is most likely to transition from laminar flow to turbulent flow. [CO3/PO2/C4] (10 marks) Properties of Air: v = 1.5 x 10-5m2/s and p 1.2 kg/m3