How Is Current Calculated for Rotational Equilibrium in a Magnetic Field?

[TheBigDig]

1. A uniform bar has mass 0.0180 kg and is 30.0cm long. It pivots without friction about an axis perpendicular to the bar at point a (as seen in the diagram). The gravitational force on the bar acts in the −y-direction. The bar is in a uniform magnetic field that is directed into the page and has magnitude 0.350 T . What must be the current I in the bar for the bar to be in rotational equilibrium when it is at an angle 60.0^o above the horizontal? 2. F = qv x B
dF = Idl x B3. I've attempted to just plug in the values using the numbers given in the question but I'm unsure how to account for the angle using the above formulae.

 

[David Lewis]

Draw a free-body diagram. Show all the forces acting on the bar.

 

[TheBigDig]

Thanks. Found it by equating mg(L/2 cos theta) to IB L^2/2 and solving for I.