The radius of the earth is `6400 km` and `g=10m//sec^(2)`. In order that a dody of `5 kg` weight zero at the equator, the angular speed of the earth is

Options

A. `(1)/(80)` radian/sec.
B. `(1)/(800)` radian/sec.
C. `(1)/(200)` radian/sec.
D. `(1)/(400)` radian/sec.

Answer

B

Explanation

`mR omega^(2)=mg`
`therefore omega = sqrt((g)/(R ))=sqrt((10)/(6400xx10^(3)))=(1)/(800)` rad/s