Question

Two point masses at a given distance exert a gravitational interaction force on each other having a magnitude F. If one mass is doubled the other mass is halved and the distance between them is tripled, the resulting interaction force magnitude.
(a) F (b) 4F (c) 4F/9 (d)F/9

Answer 1

F = GmM/r²

F = G (2m)(M/2)

(3r)²

Both 2s get cancelled out and

The value of (3r)² = 9r²

Separate the 9 from the equation to get -

GmM

r² × 1/9

And then put the values

F × 1/9 = F/9 is your answer.