I have attempted to use 2 different formulas, but I can\'t seemto make them work

Question

I have attempted to use 2 different formulas, but I can't seemto make them work. The problem says: An electron starts from rest3cm from the center of a uniformly shaped sphere with radius 2 cm.If the sphere carries the charge 1.00x10^-9 C, how fast will theelectron be moving when it reaches the surface of the sphere. I have attempted to use Vf^2 - deltaPE = 0 and deltaKE = qEdbut each one has a component that I can't figure out! I have attempted to use 2 different formulas, but I can't seemto make them work. The problem says: An electron starts from rest3cm from the center of a uniformly shaped sphere with radius 2 cm.If the sphere carries the charge 1.00x10^-9 C, how fast will theelectron be moving when it reaches the surface of the sphere. I have attempted to use Vf^2 - deltaPE = 0 and deltaKE = qEdbut each one has a component that I can't figure out!

Explanation / Answer

Using PE is correct - you can't use q E d because E isnot constant and you would need to use calculus for that approach PE = 1/2 m v2 = K Q q / .02 - k Q q / .03 = kQ q (1 / .02 - 1 / .03) = -16.67 k Q q (The decrease in PE is converted to KE) Then 1/2 m v2 = 16.67 k Q q v = [(33.33 * 9 * 10E9 * 1 * 10E-9 * 1.6 *10E-19) / 9.1 * 10E-31)] v = (33.33 * 9 * 1.6 / 9.1) * 10E6 = 7.26 * 10E7m/s

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