18.7. Set Up: For a pair of point charges the electrical potential energy is In the O-H-O combination the is 0.180 nm from the and 0.290 nm from the other In the N-H-N combination the is 0.190 nm from the and 0.300 nm from the other U is positive for like charges and negative for unlike charges. In the O-H-N combination the is 0.180 nm from the and 0.290 nm from the U is positive for like charges and negative for unlike charges. Solve: O-H-O N-H-N O-H-N The total potential energy is Reflect: For pairs of opposite sign the potential energy is negative and for pairs of the same sign the potential energy is positive. The net electrical potential energy is the algebraic sum of the potential energy of each pair. 18.8. Set Up: The initial potential energy is converted to kinetic energy after the charges have moved far apart. Apply to each pair of charges and add to get the total electrical potential energy. In part (b) the distance between the and charges is 18.0 cm. Solve: (a)
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