If the value of `g` at the surface of the earth is `9.8 m//sec^(2)`, then the value of `g` at a place `480` km above the surface of the earth will be (Radius of the earth is `6400` km)

Options

A. `8.4m//s^(2)`
B. `9.8m//s^(2)`
C. `7.2m//s^(2)`
D. `4.2m//s^(2)`

Answer

a

Explanation

`g prop (1)/(R^(2)) and g' prop (1)/((R+h)^(2))`
`therefore" "g'=g(R^(2))/((R+h)^(2))=8.4m//s^(2)`