1. The problem statement, all variables and given/known data A small ball has a mass of mass m 4.0 x 10^-8 kg and a charge of q = -2.0 x 10^-5 C. It enters a box with an initial speed of v0 = 1.0 x 10^4 m/s. The point where the charge leaves the box is at a voltage 350 kV higher than the entry point. 2. Relevant equations 1/2mv^2(f)-1/2mv^2=qV(f)-qV(i) 3. The attempt at a solution 1/2(4.0 x 10^-8)v^2-1/2(4.0 x 10^-8)(1.0 x 10^4)=q(V(f)-V(i)) 1/2(4.0 x 10^-8)v^2-1/2(4.0 x 10^-8)(1.0 x 10^4)^2=-2.0x10^-5(3.5x10^5) 1/2(4.0 x 10^-8)v^2-(2)=-7 <-- there is were it all falls apart as you can see i will end up with a (-) under the sqrt and that is just a fail. I understood everything in physics right up until EP and now the emails i get from my professor are just useless. thanks for your help in advance. i am assuming that the 350kv is the V(f)-V(i) is this wrong?