review for exam#1-1

review for exam#1-1 - Review for exam #1 Chapter 21 #8 In...

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Unformatted text preview: Review for exam #1 Chapter 21 #8 In Fig. 21-23, four particles form a square. The charges are and . (a) What is if the net electrostatic force on particles 1 and 4 is zero? (b) Is there any value of q that makes the net electrostatic force on each of the four particles zero? Explain. 8. 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 ( 29 ( 29 ( 29 ( 29 ( 29 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 =-0 + =- + 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 ( 29 ( 29 ( 29 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. Chapter 21 #28 Two tiny, spherical water drops, with identical charges of , have a center-to-center separation of 1.00 cm. (a) What is the magnitude of the electrostatic force acting between them? (b) How many excess electrons are on each drop, giving it its charge imbalance?...
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review for exam#1-1 - Review for exam #1 Chapter 21 #8 In...

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