# Finding the final velocity of a proton

## Homework Statement

A charged particle (either an electron or a proton) is moving rightward between two parallel charged plates separated by distance d = 1.90 mm. The particle is slowing from an initial speed of 93.5 km/s at the left plate. The left plate has V=-70V and the right plate has V=-50V

q=1.602e-19 C
m=9.11e-31 kg

## Homework Equations

Conservation of Energy:
U_2+1/2mv_1^2=U_2+1/2mv_2^2
U=Vq

## The Attempt at a Solution

Alright, so I just used the conservation of energy, assuming that the energy at the right plate will equal the energy at the left plate. Rearranging that equation I solved for v_2. However, I always get a nonreal answer. I tried this problem again using kinematics and solving for the force then the acceleration using E=-V/d=F/q and F=ma and I got the same negative number within the square root. Someone please solve this and tell me if it's possible. Then let me know where I'm going wrong! Thanks!

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tms
What is the problem asking for?

Show your work; no one can tell what you may have done wrong if they can't see what you did.

Nevermind, I figured it out. I was using the mass for an electron and not for a proton.

tms
What's a factor of 1800 among friends?