Mastering Physics Solutions: Exercise 16.10

Exercise 16.10

Part A = -2.3 J Click to use the calculator/solver for this part of the problem

Solution Below:

Part A

How much work is required to completely separate two charges (each -1.5 μC) and leave them at rest if they were initially 9.0 mm apart?
Express your answer using two significant figures.

Work = change in electric potential. The formula for electric potential is given by V = (k * q1 * q2) / r. Note that the work will be negative since like charges repel:

W = (k * q1 * q2) / r
W = 8.9875 * 109 * -0.0000015 * -0.0000015 / 0.009
W = 2.246875 J

Round to 2 significant figures and make negative since the charges are repelling each other:

W = -2.2 J

Note: Mastering Physics took -2.3 J as the answer for me. It’s a rounding type issue because Mastering Physics sometimes uses a Coulomb Constant of 9 * 109 instead of the more correct 8.9875 * 109

-2.3 J

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