Extracted text: Q.48 The internal diameter of a shaft of steel is 70% of the external diameter. The shaft is to transmit 3500 kW at 200 rpm. If the maximum allowable stress in the shaft material is 50 MPa, calculate the diameter of the shaft. Find also the maximum twist of the shaft when it is stressed to the maximum permissible value. The length of the shaft is 4 m. Take G = 80 MPa.