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Unformatted text preview: 1 Class Examples for Chapter 21 10. For ease of presentation (of the computations below) we assume Q > 0 and q < 0 (although the final result does not depend on this particular choice). (a) The x-component of the force experienced by q 1 = Q is 1 2 2 2 | | 1 | | / | | cos45 1 4 4 2 2 2 x Q Q q Q Q q Q q F a a a which (upon requiring F 1 x = 0) leads to / | | 2 2 Q q , or / 2 2 2.83. Q q (b) The y-component of the net force on q 2 = q is 2 2 2 2 2 2 | | 1 | | | | 1 sin 45 4 4 | | 2 2 2 y q Q q q Q F a a q a which (if we demand F 2 y = 0) leads to / 1/ 2 2 Q q . The result is inconsistent with that obtained in part (a). Thus, we are unable to construct an equilibrium configuration with this geometry, where the only forces present are given by Eq. 21-1. 16. (a) According to the graph, when q 3 is very close to q 1 (at which point we can consider the force exerted by particle 1 on 3 to dominate) there is a (large) force in the positive x direction. This is a repulsive force, then, so we conclude q 1 has the same sign as q 3 . Thus, q 3 is a positive-valued charge. is a positive-valued charge....
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This document was uploaded on 11/04/2011 for the course PHY 108 at SUNY Buffalo.
- Fall '08