1. Select the diameter of a solid circular steel shaft for a motor that produces 7.5 kW operating at 1800 r/min. The allowable shear stress in the shaft is 50 MPa.
2. Select the diameter for a hollow steel shaft that is to transmit 36 hp at 1200 rpm. The allowable shear stress is 9000 psi, and the inside diameter of the shaft is to be three-fourths of the outside diameter.