Find the magnitude of the gravitational field

[matt_crouch]

Homework Statement

Find the magnitude of the gravitational field a distance r from an infinitly long uniform thin rod whose mass per unit length is (lamda)

Homework Equations

The Attempt at a Solution

Need some clarification really
i know

dgx=-Gdm/r²

r=r₂-r₁

lamda=m/L

i substituded them in and intergrated

so to finally get

=-GM/r₂²-r₁²

 

[kuruman]

You need to show the details of what you did. Otherwise it is hard to figure out what you did wrong. However, your final answer must be in terms of lambda r and G. There should be no M (the mass of the rod is infinite) or r₁ and r₂ (there is only one r, the distance of the point of interest to the rod).