Compute all parts of given problem:
Problem: A charged particle travels unelected through perpendicular electric and magnetic fields whose magnitudes are 4000N/C and 40mT, respectively.
Part I: Find the speed of the particle if it is a proton?
Part II: Find the speed of the particle if it is an alpha particle. (An alpha particle is a helium nucleus-a positive ion with a double positive charge of +2e.)
Please provide a full detailed explanation for the solution.