Four charges are at the corners of a square centered at the origin as follows:
q at (-a , +a); 2q at (+a , +a); 3q at (+a , -a) and 6q at (-a , -a).
A fifth charge +q is placed at the origin and released from rest.
Find its speed when it is a great distance from the origin if a = 0.6 m, q = 3.8 mC and its mass is 0.8 kg.

If the speed of a particle triples ,by what factor does its kinetic energy increase?

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?

Which system of units is used by only a small number of countries in the world, including the u. s.