Ice-cream Posted June 29, 2005 Posted June 29, 2005 "A point charge q = -0.35nC is fixed at the origin. Where must an electron be placed in order for the electric force acting on it to be exactly opposite to its weight? (Let the y axis be vertical and x axis be horizontal)" [ans: 240km above q] my question is, i've found 240km using coloumb's law...but im not sure about the direction...how com the answer is 240km "above q"??
Yggdrasil Posted June 29, 2005 Posted June 29, 2005 Both the point charge and electron are negatively charged. Therefore, the electric force between them is repulsive. Since the gravitational force acts in the negative y dirrection, the electric force must act in the positive y dirrection for them to cancel. For that to happen, the electron must be above q.
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