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## Homework Statement

A ring of charge is situated in the x‐y plane centered about the origin. The ring has a

uniformly distributed charge Q = ‐10 nC and a radius R = 2.0 cm.

a. Find the electric potential at a distance z = 5.0 cm above the origin on the z=axis.

b. Find the electric field at a distance z = 5.0 cm above the origin on the z=axis.

c. Find the speed of a proton as it passes through the origin assuming that it is

released from rest at z=5.0 cm.

## Homework Equations

λ=Q/l

dl=RdΘ

dq=λdl

E(z)=KQx/(x^2+R^2)^3/2

U= KQq/r

## The Attempt at a Solution

After solving to get this

b) E(z)=KQx/(x^2+R^2)^3/2

=(8.998x10^9)(10x10^-6)(0.05m) / (0.05^2+0.02^2)^3/2

=2.88x10^7 N/C

Now I feel like this is really easy to get a, but I can't seem to get it. And c is just blew my mind.