9.1 Relative velocities are an important concept in the analysis of turbomachines. To help understand relative velocity, consider that a baseball is thrown at a moving train as shown in Fig. P9.1. If the baseball has a velocity of 60 mph and the train is traveling at 80 mph, find the magnitude and direction of the baseball velocity relative to the train.

Figure P9.1

9.2 A small fan used to circulate air in a room is shown in Fig. P9.2. The fan blades are twisted and change their angle relative to the centerline of the fan as the radius increases. If the relative velocity of the air makes the same angle to the centerline of the fan as the blades and if the blade at a radius of 0.2 m has an angle of 60 deg, determine the speed of the air for fan speeds of 1725 and 3450 rpm.

Figure P9.2

9.3 Air flows through an axial compressor stage with the following properties:

Note: For air, use ? = 1.4 and R = 0.286 kJ/(kg K). Determine the change in tangential velocity and the total pressure ratio of the stage for a stage efficiency of 0.88.

9.4 Air flows through an axial compressor stage with the following properties:

Note: For air, use ? = 1.4 and R = 53.34 ft lbf/(lbm R). Determine the change in tangential velocity and the total pressure ratio...