Problem 1: A ring of radius R = $10-3 m carries a charge of @ = -, x 10 " C. If a single ionized xenon atom (q = 1e) is released from rest 10 millimeters from the ring, along the axis of the ring, what would its speed be as it crossed through the center of the ring? You can get the mass of a xenon atom from the appendix of your book or periodic table. First find the change in electric potential energy, or the final kinetic energy in terms of electron volts, ev. Then convert to Joules in the process of finding the speed. Answer in kilometers per second. This problem is very similar to the calculation for the speed of an ion in an ion-engine used on interplanetary missions