1.The safe twisting moment for a compound shaft is equal to the

2.Shear stress induced in a shaft subjected to tension will be

3.The torsional rigidity of a shaft is expressed by the

4.In a belt drive, the pulley diameter is doubled, the belt tension and pulley width remaining same. The changes required in key will be

5.A key is subjected to side pressure as well at shearing forces. These pressures are called