# Homework Help: Velocity of electrons

1. Jul 25, 2011

### Punch

1. The problem statement, all variables and given/known data

A beam of electrons, with kinetic energy of 500eV, enters mid-way into the space between two oppositely charged parallel plates with a potential difference of 100V

2. Relevant equations

Determine the velocity of the electrons

3. The attempt at a solution

KE=0.5mv^2
500(1.60x10^-19)=0.5(500 x 9.11 x 10^-31)(v^2)
v=5.93x10^5

2. Jul 25, 2011

### Clever-Name

First, this isn't really advanced physics, this should be in the introductory physics section.

Second, I have no idea what you did with your equation work. Why is there a 500 term in the mass for the electron? There is only 1 electron, in the beam there may be multiple electrons, but each one carries the same energy.

Also, determine the velocity WHERE? It will be different at different points throughout the apparatus.

Last edited: Jul 25, 2011
3. Jul 26, 2011

### cupid.callin

what is that 500 doing there?

you have just found initial velocity (though it has a small error as i said above)

you also need to calculate the new velocity perpendicular to plates ... which depends on how far electrons have moved b/w the plates.