1. The problem statement, all variables and given/known data A uniform electric field exists in the region between two oppositely charged parallel plates (1.64*10-2)m apart. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval (1.60*10−6)s. Find the speed of the proton at the moment it strikes the negatively charged plate. 2. Relevant equations [tex]x = x_0 + v_0 t + (1/2) a t^2[/tex] [tex]v = v_0 + a t[/tex] [tex]v^2 = v_0^2 + 2 a (x - x_0)[/tex] 3. The attempt at a solution Okay so I found a by using this equation ([tex]x = x_0 + v_0 t + (1/2) a t^2[/tex]) and it came out to be 1.2812*10^10. To find velocity when it hits, I realized that I get a different answer when I use this ([tex]v = v_0 + a t[/tex]) and that ([tex]v^2 = v_0^2 + 2 a (x - x_0)[/tex]). The correct answer came out when I used the latter equation. So my question is, why is it that I can't use the first equation? Shouldn't they come out to be the same answer? Did I do something wrong? Thanks guys.