# Homework Help: Physics Question about an electron

1. Sep 27, 2007

### SMUDGY

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I need help on this physics question:

An electron is shot at 10^6 ms-1 between two parallel charged plates. if (e) = 1 KN/C where will the electron strike the upper plate? Assume vacuum conditions.

I think i need to use a motion eqauation but which one.

2. Sep 27, 2007

### JoAuSc

What does "(e)" refer to? Do we know how wide apart the plates are?

3. Sep 27, 2007

### genneth

There is only one equation of motion: F=ma.

You need to work out what the forces are, and adopt a sensible coordinate system so that you can talk about acceleration, velocity and displacement in a reasonable way. So in this case, choose something with one of the axes going along the direction of the electric field, and one along the initial direction of the electron. Then you can work out what the force on the electron is, and solve the resulting (differential) equation.

4. Sep 27, 2007

### drpizza

What do you know about the electric field between two parallel charged plates?

Can you calculate the force that the electron experiences?

However, at this point, I now have the same question as JoAuSc: How far apart are the plates? (And, I'll assume the electron is shot in the center between the plates.)

5. Sep 28, 2007

### SMUDGY

aparently you don't need to know the distance apart and (e) is an electron which is 6.11 x 10e-16 or something.

There are other motion equations such as a=v-u/t etc

i,ve drawn it out but still doesnt make sense to me like its lacking detail but i havent got anything missing