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

Options

A. `(2)/(5)(pi^(2)n^(2)r^(2))/(c)`
B. `(1)/(10)(pi^(2)n^(2))/(r^(2)c)`
C. `(7)/(8)pir^(2)n^(2)c`
D. `(1)/(8)(pi^(2)n^(2)r^(2))/(c)`

Answer

A