The field between the plates of a parallel plate capacitor, $E=Q /\left(\epsilon_{0} A\right),$ is due to the superposition of equal contributions from the charges on the two plates. Therefore, each plate exerts an electric force on the other. (a) Find the magnitude of this force in terms of
(b) Suppose the plates have no other $Q, \epsilon_{0},$ and $A$ forces acting on them and they start a distance $d$ apart. Find the kinetic energy of each plate when they collide. [Hint: Two different methods are possible.]