A string of length 1m is fixed at one end and carries a mass of 100 g at other end . The string makes `(2//pi)` revolutions per second around verti9cal axis through the fixed end . (Take `g=10 m//s^(2)`)
The angle of inclination of the string with the vertical is

Options

A. `cos^(-1)(8//5)`
B. `cos^(-1)(5//8)`
C. `sin^(-1)(8//5)`
D. `sin^(-1)(5//8)`

Answer

B

Explanation

From eq . (1) `cos theta = (mg)/T =(10^(-1)xx10)/(1.6) =5/8`
ie, `theta = cos^(-1) (5//8)`