an engineer plans to analyze the drag force acting on a chemical plant flue-gas stack, i.e., an exhaust chimney. a 1:10 scale model of the 60 ft tall stack is placed in a wind tunnel for testing. the air speed around the real stack is estimated to be 20 mph. a. assuming the same air properties, what should be the air speed used in the wind tunnel for testing? b. if the drag force on the model stack is 1000 lbf , what would the drag force be on the real flue-gas stack?