1. The problem statement, all variables and given/known data A proton travelling along the x-axis is slowed by a uniform electric field E. At x = 20 cm, the proton has a speed of 3.5 x 106 ms-1 and at x = 80 cm, its speed is zero. Find the magnitude and direction of electric field intensity. Can someone please!!!! check my procedure and if your really nice/helpful my answer-----thanks. 2. Relevant equations W=Fx W=Eqx W=ΔK_E ΔK_E=1/2 mv^2-1/2 mu^2 3. The attempt at a solution 1st i found the change in energy (work) to slow the proton to a stop. then thats equal to Eqx. I found E to be 1.06*10^5 N/C (positive direction) please check my answer if you have time - its worth marks.