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coloumb's law


Ice-cream

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"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"??

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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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