A set of point charges is held in place at the vertices of an equilateral triang

Question

A set of point charges is held in place at the vertices of an equilateral triangle of side 10.0 cm , as shown in (Figure 1) .

Part A

What is the electric potential energy of the 3.00 nC charge?

Express your answer in joules to three significant figures.

Part B

What would be the maximum kinetic energy of the 3.00 nC charge if it were released from rest in the frictionless void of outer space? (Assume the other charges are held in place.)

Express your answer in joules to three significant figures.

Part C

When will this maximum kinetic energy be achieved, just following the release of the charges or after a very long time?

When will this maximum kinetic energy be achieved, just following the release of the charges or after a very long time?

or
__ after a very long time

or
__ after a very long time

Explanation / Answer

final KE = initial PE
First we find total initial potential energy.
Total PE is the sum of the three PE values between the charge pairs
For one pair PE = kq1q2/r (where k=9E9 Nm^2/C^2).
For three pairs we have PE = 9E9(q1q2+q1q3+q2q3)/0.1 J
= 9E9*((-4E-9*-2E-9) + (-2E-9*-3E-9) + (-4E-9*-3E-9))/0.1 J = 2.34E-6 J
KE = 2.34E-6 J

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