1. Through what potential difference would an electron need to be accelerated for it to achieve a speed of 50.0% of the speed of light, starting from rest? The speed of light is c = 3.00 108 m/s. >> I'm really not too sure what to do with this problem. I took .50*3.00e8 and got 1.50e8. Then I said deltaV = Vb-Va = 1.50e8 - 0 and got 1.50e8 as my answer. But that doesn't seem right... I'm confused :( 2. Two charges Q1 = Q2 = 2.50 µC are positioned along the x-axis, where Q1 is at point (-.800m, 0) and Q2 is at point (+.800, 0), with a positive test charge q = 1.22e18 C at the origin. (a) What is the net force exerted on q by the two 2.50 µC charges? (b) What is the electric field at the origin due to the two 2.50 µC charges? (c) What is the electrical potential at the origin due to the two 2.50 µC charges? >> I know for part (a) the answer must be 0 because they cancle each other out. I also know that for part (b) the answer must be 0 because the fields will be repelled. Part (c) I'm stuck on... I tried Vp=Ke(q1/r1 + q2/r2) and got Vp=(8.99e9)(2)(2.50e-6/.8) and a final answer of 5.62e13. But that's not right... how should I solve part c??