1. The problem statement, all variables and given/known data An infinitely long cylinder of radius a in free space is charged with a volume charge density ρ(r) = ρ0*(a-r)/a (0 ≤ r ≤ a), where ρ0 is a constant and r the radial distance from the cylindrical axis. Find the charge per unit length of the cylinder. 2. Relevant equations Qpul = Qalong l/l 3. The attempt at a solution I'm pretty sure I'm supposed to integrate in cylindrical coordinates, however, it has been a while since I have done so. The limits of integration should be 0 to a. The equation for ρ0 is being integrated. But I thought there was something you're supposed to do when integrating in cylindrical. Or maybe it would actually be better in rectangular? Though I doubt that.