Electrostatics

閣下的計算之問題在於: a 不是 constant, 因為隨著距離的縮短, electric force 亦會增強, 即 a 亦會增加, 於是 v2 - u2 = 2as 在 a = constant 的大前題下便不能使用了.
其實, 取而代之我們應該考慮 potential energy loss = kinetic energy gain:
Potential energy loss:
Q1Q2/4πε0 [1/(0.1) - 1/(1)] = 8.093 × 10-4 J
So kinetic energy gain should be of this value:
0.5 × (2 × 10-5) × v2 = 8.093 × 10-4
v = 9.0 m/s