A hoop is hung on the wall by a nail attached to the very edge at the top. If the mass of the hoop is 5 kg and the radius is 30 cm, find the rotational inertia of the hoop about the nail. Ihoop = MR2

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?