QUESTION $3$

a$.$ Find the external and internal diameters required for a hollow shaft which is to transmit $40$

KWatt of power at $240re\frac{v}{?}$ minute. The shear stress is to be limited to $100M\frac{N}{m^2}.$ Take

external diameter to be twice the internal diameter.

b$.$ A vertical rod of length $3$ m tapers uniformly from a diameter of $80$ mm at top to $40$ mm at

the bottom. If it is rigidly fixed at the upper end and is subjected to an axial load of $45$ KN $,$

determine the total extension in the bar. Take the density of the material $=2{10}^{5}k\frac{g}{m^3}$ and

Young's modulus $=210G\frac{N}{m^2}.$