Astudent needs to measure the drag on a prototype of characteristic length dp moving at velocity up in air at sea-level conditions. he constructs a model of characteristic length dm, such that the ratio dp/dm = a factor f. he then measures the model drag under dynamically similar conditions, in sea-level air. the student claims that the drag force on the prototype will be identical to that of the model. is this claim correct? explain.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2