An electron is released from rest on the axis of a uniform positively charged ring, 0.200 m from the ring's center. if the linear charge density of the ring is 0.100 µc/m and the radius of the ring is 0.400 m, how fast will the electron be moving when it reaches the center of the ring?

Velocity of the electron at the centre of the ring,

Explanation:

Given:

Total charge of the ring

Potential due the ring at a distance x from the centre of the rings is given by

The potential difference when the electron moves from x=0.2 m to the centre of the ring is given by

Let be the change in potential Energy given by

Change in Potential Energy of the electron will be equal to the change in kinetic Energy of the electron

So the electron will be moving with

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.