# physics

two positive points charges of 15c and 13c are placed 12cm apart . find the work done in bringing the two charges 4cm closer.

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1. find the Potential energy at one of the charges due to the distance and othter charge.

PE=kQ1Q2/d

What is the PE at 4 cm closer?

PE=kQ1Q2/(d-.04)

then thw work moving Q2 must be

difference in PE

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2. W=u¹+u²

u¹=kq¹q²/d

u²=kq¹q²/d-0.5

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