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Homework Statement
A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force:
a) does positive work and increases the kinetic energy of the small sphere
b) does negative work and increases the kinetic energy of the small sphere
Homework Equations
The Attempt at a Solution
( + ) ----> (+)So the electrostatic force is pushing the smaller charged force away. It looses potential energy and converts it into kinetic energy. Since W = (delta) (Kinetic energy) and kinetic energy increases, Ek > 0
Movement is also in the direction of the electric field (cos0) = 1 therefore it should be positive (as far as I know)
Work should be positive, the answer should be A)
However, the answer is B). Why?
It doesn't mathematically make sense to me. I've proven that W = change in kinetic energy.
However, when I conceptually think about it it makes sense that work is negative- because it's the same thing as a mass falling from a height- negative work is done on it.
Is this physics? Will it be full of exceptions and mathematical fallacies?
It seems like physics is turning more and more into a computer script
if case 1: do this algorithm
if case 2: do that algorithm
Is that it? Will I just have to just memorize these exceptions as I go along in physics, or is there another way of looking at it?
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