Question

A positively charged disk of radius R and total charge Qdisk lies in the xz plane, centered on the y axis (see figure below). Also centered on the y axis is a charged ring with the same radius as the disk and total charge Qring. The ring is a distance d above the disk. Determine the electric field at the point P on the y axis, where P is above the ring a distance y from the origin. (Use any variable or symbol stated above along with the following as necessary: k.)

Answer 1

Everything is correct except the last term in the denominator where it should be R^{​​​​​​2} instead of k^{​​​​​​2.}