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I tried this problem for three hours and I feel like I cantget the right answer.

ID: 1760541 • Letter: I

Question

I tried this problem for three hours and I feel like I cantget the right answer. Heres the problem:
Three identical positive point charges are located at the verticesof an equilateral triangle. If the length of each side of thetriangle shrinks to one-fourth of itsoriginal length, by what factor does the electrostatic potentialenergy of this system change? (The electrostatic potential energyapproaches zero if the length of each side of the triangleapproaches infinity.)

I tried this problem for three hours and I feel like I cantget the right answer. Heres the problem:
Three identical positive point charges are located at the verticesof an equilateral triangle. If the length of each side of thetriangle shrinks to one-fourth of itsoriginal length, by what factor does the electrostatic potentialenergy of this system change? (The electrostatic potential energyapproaches zero if the length of each side of the triangleapproaches infinity.)

Explanation / Answer

each pair of charges has potential energy givenby    PE = k q1 q2 /d       where d is thedistance between them. . If each leg shrinks by a factor of 4, then d is smaller forall pairs of charges by a factor of 4, so each pair of potentialenergy is greater by a factor of 4. .     So the total potential energy of the systemincreases by a factor of4.