1. The problem statement, all variables and given/known data consider a parallel-plate capacitor with square plates of side L and distance d (<<L) between them, charged with charges +Q and -Q. The plates of the capacitor are horizontal, with the lowest lying on the x-y plane, and the orientation is such that their sides are parallel to the x and y axis, respectively consider a simple pendulum of length d/2 and mass m, hanging vertically from the centre of the top plate, that can oscillate in the x-z plane. Calculate the electric field inside the capacitor, and the electrical force acting on the mass if it has charge q (the field produced by the charge q itself can be neglected, and the polarity of the capacitor is such that the force will act in the negative z direction). 2. Relevant equations E=-grad V =[q/(4pi*epsilon0)][1/(r^2)]*(r-hat) 3. The attempt at a solution should i just use the above equation, and sort of ignore the r-hat at the end? would the answer to what the electric field is be zero? then would the electrical force be F=Bqv? but what would i put in for B and v?