A uniformly charged disk (radius R and surface charge density +1.70 µC/m2) lies in the xy plane with its center at the origin. The marked point P is exactly a distance R above the center of the disk. An electron is to be released from rest at several points along the z axis
a) what is the electron's initial acceleration if it is released at point P?
b) if it is released (1/100)th of the way from the disk to point P?
c) if it is released (1/1000)th of the way from the disk to point P?