particle collision/response

hi ive been working with opengl for a bit now, but i am not incredibly experienced with programming in general. Right now im working on a particle system that is supposed to simulate the introduction of particles into a chamber through a nozzle like device. I use a cylinder for the nozzle, and basically just have the particles explode in the center of it. I think I have the particle detection figured out (though any suggestions on how someone more experience might do it are welcome), but Im not sure how to do the particle response calculations when they collide with the cylinder. Any advice or help is much appreciated