John is running around the field. His first lap took 30 seconds to complete and he slowed down his pace during his second lap, which took him 45 seconds. If the distance of one round of field is 200m, calculate the acceleration of John.

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?