A solid shaft of $20\text{ cm}$ diameter has the same cross – section…

Question

A solid shaft of $20\text{ cm}$ diameter has the same cross – sectional area as a hollow shaft of the same material with inside diameter of $15\text{ cm}$.

(a) Find the ratio of horse powers transmitted by the two shafts at the same angular velocity.

(b) Compare the angles of twist in equal lengths of these shafts, when stressed to the same intensity.