What is the gravitational force of attraction between a particle and a rod?

[tech_guru]

OK...this must b simple...but I don't know how to go 'bout...it needs some integration for sure...I have also attached the diagram with it.

Find the gravitation force of attraction between a particle of mass m and a uniform slender rod of mass M and length L for the orientation given in the diagram.Thed istance between the particle and the rod is D.


The answer should come out to be-

[2GmM]/[D{L^2 + 4 D^2}^0.5]

 

[thequirk]

I can't see the picture, but what you generally do in problems like this is break apart the rod into small pieces (dL), find the contribution of one piece to the force (dF), and then integrate. The mass of this small piece will be (M/L)dl, since M/L is the linear density (I'm assuming that the rod has uniform density).