Problem 4 [Marks 2.0] The aerodynamic drag of a new sports car is to be predicted at a speed of 100 km/h at an air temperature of 25°C. Automotive engineers build a 1:2 scale model of the car to test in a wind tunnel. The temperature of the wind tunnel air is also 25°C. The drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground (from the car's frame of reference). The aerodynamic drag on the model in the wind tunnel is measured to be 200 N. Determine: Wind tunnel test section Moving belt Drag balance FD.m 1) How fast (in km/h) the engineers should run the wind tunnel to achieve similarity between the model and the prototype. 2) The aerodynamic drag force (in N) on the prototype car if the drag force on the model is measured to be 200 N when the wind tunnel is operated at the speed that ensures similarity with the prototype car.

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