1. The problem statement, all variables and given/known data What is the speed of a proton after being accelerated to a kinetic energy of 750keV? 2. Relevant equations E=K+E0 E0=mc^2 K=(gamma-1)mc^2 gamma=1/(sqroot(1-v^2/c^2)) 3. The attempt at a solution Alright, so to find the speed, I used the equation: K=(gamma-1)mc^2 which i simplified to: 1/(gamma-1)=mc^2/K I converted K into joules which is equal to 1.202E-13 J and what I ended up getting was that sqroot(1-v^2/c^2) - 1=1250.42 but if i continue on with that I will need to take the square root of a negative number because i will bring v^2/c^2 to the right side and then I would have to do 1-1250.42 and take the square root of that which is undefined. Any help would be great!!!