Two parallel plates X and Y are separated by a distance d in a vacuum

Two parallel plates X and Y are separated by a distance d in a vacuum. There is a potential

difference between the plates so that a uniform electric field is produced.

                   

Two parallel plates X and Y are separated by a distance d in a vacuum

A charge –q moves from rest from the surface of plate X and travels towards plate Y.

When the charge reaches plate Y it has kinetic energy K.

Which expression gives the electric field strength between the plates?