I have a circle emiting particles up a column. However, I want it to curve down towards the ground as though effected by gravity. I added a sideways force, but it seems to only angle the particles trajection from the emiter. Solution?
Also, is there a way to make one end more dense than another in a particle system?
Keep the side force on the particle system, but add a “NOR” force using the NOR slider above the regular force buttons.
In my version of blender there is no Nor slider in the animation buttons. I cant find a Nor button even. The closes thing is Norm but that seems to just change spread.
Oh, I see the problem (besides my senility- I did mean the Norm button- which isn’t a slider at all- oh well 8) ). What I said earlier works fine with a plane, but not with a circle.
I think I found a viable workaround. Move the cursor to a couple units past where the particles disappear. If you wish (and I would recommend) use snap cursor to grid. Now, go to edit buttons with the circle selected and click “Center Cursor.” Now, in the animation buttons, change Norm to about -0.1 and give a Z force of -0.010 (or whatever looks best). Be wary of changing the Norm value, cause it might cause the particle stream to narrow quite a bit. Mess around with rotating all the vertices of the emitter in edit mode - to avoid moving the center. Also adjust the center - it might need to be far away from the vertices.
Hope this works for ya- I don’t want to steer you wrong. 
I see the road to mastering particles is long and many with blender. Properties change even depending on the emitter!
Thats what the “Norm” setting does. It the relative amount the vertex normal effects the particle’s initial velocity.
“Ob” is the amount the object’s velocity effects the particles,
“Tex” is the texture’s effect
“Rand” is a random velocity
“Damp” is the speed the particle slows down after being emitted.
Forces are always in Global Coords. To go down, use -Z force.
Bob