Magnetic field from point source

[Maxwellkid]

Homework Statement

A circular loop of wire of radius R carries current I. It is placed in a magnetic field whose straight lines seem to diverge from a point a distance d below the ring on it's axis. It makes an angle theta with the loop at all points where (tan theta= R/d). What is the force on the loop?

Homework Equations

F= IL x B

The Attempt at a Solution

I can't seem to cancel out the x and y components as I take the integral.

 

[tiny-tim]

Hi Maxwellkid!

… I can't seem to cancel out the x and y components as I take the integral.

Two practical answers:

a) why bother? you know it'll be in the z direction, so just do the z component!

b) but if you are bothered, show us what you did, and where it goes wrong