What is the arrangement of net gravitational force on a particle labeled m?

[duoshock]

Hi,

I attached a diagram... to find out the arrangement of the magnitude of the net gravitational force on the particle labeled m from the smallest to the biggest.

my answer is A B D C, anyone had a different way of looking at it?
could you explain? some of my friends said it was A D B C... =|

Thanks in advance
duoshock

 

[HallsofIvy]

In B, there is one mass at distance d, the other at distance D.
In D, there is one mass at distance d, the other at distance $\sqrt{d^2+ D^2}$.

The force from the mass at distance D will be greater than the force from the mass a distance $\sqrt{d^2+ D^2}$ so the net force in B is greater than in D.

 

[duoshock]

i give D a value of 50 and d a value of 1 and my result is square root of (d^2 + D^2) is more than D. My maths isn't very good. Could you help to explain?

Thanks