A small body of superdense material, whose mass is twice the mass of the earth but whose size is very small compared to the size of the earth, starts form rest at a height `H lt lt R` above the earth's surface, and reaches the earth's surface in time `t`. then `t` is equal to

Options

A. `sqrt(2H//g)`
B. `sqrt(H//g)`
C. `sqrt(2H//3g)`
D. `sqrt(4H//3g)`

Answer

C

Explanation

As the masses of the body and the earth are comparable, they will moves towards their centre of mass, wheich remains stationary.
Hence th ebody of mass 2 m move through distance H/3.
and time to reach the earth surface
`=sqrt((2h)/g)=sqrt((2H//3)/g)=sqrt((2H)/(3g))`