A metal sphere of radius r and specific heat s is rotated about an axis passing through its centre at a speed of n rotations per second. It is suddenly stopped and `50%` of its energy is used in increasing its temperature. The the rise in temperature of the sphere is

Options

A. `(2pi^2n^2r^2)/(5s)`
B. `(pi^2n^2)/(10r^2s)`
C. `(7/8)pi^2r^2n^2s)`
D. `(5(pirn)^2)/(14s)`

Answer

A