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:

Explanation

Position of null point from mass `m` is
`x=r/(sqrt((4m)/m)+1)=r/3`

`:. ` potential `V=-Gm(3/r+12/(2r))=(-9Gm)/r`