Two bodies of masses m and 4m are placed at a distance r. The gravitational potential at a point on the line joining them where the gravitational field is zero is:

Options

A. `-(6Gm)/(r)`
B. `-(9Gm)/(r)`
C. zero
D. `-(4Gm)/(r)`

Answer

B

Explanation

`(Gxxm)/(x^(2))=(Gxx4m)/((r-x)^(2))impliesx=(r)/(3)`
Potential at point the gravitaional field is zero between the masses.
`V=-(3Gm)/(r)-(3xxGxx4m)/(2r)`
`=-(3Gm)/(r)[1+2]=-(9GM)/(r)`