An engineering student considers using a fan as a levitation demonstation. She plans to face the box-enclosed fan
so the air blast is directed face down through a 3 ft diameter blade span area. The system weighs 5 lbf, and the
student will secure the system from rotating. By increasing the power to the fan, she plans to increase the blade rpm and air exit velocity until the exhaust provides sufficient upward force to cause the box fan to hover in the air. Determine (a) the air exit velocity to produce 5 lbf (b) the volumetric flow rate needed and (c) the minimum mechanical power that must be supplied to the airstream. Take the air density to be .078 lbm/ft^3.