57. Let the distance in question be r. The initial kinetic energy of the electron is 1 Ki = 2 me vi2 , where vi = 3.2 105 m/s. As the speed doubles, K becomes 4Ki. Thus U = or r= 3 ( 4 0 ) m v 2e 2
3 e2 = K = (4 Ki Ki ) = 3Ki = me vi2 , 4 0 r 2 = 2 (
55. (a) The electric field between the plates is leftward in Fig, 24-52 since it points towards lower values of potential. The force (associated with the field, by Eq. 23-28) is evidently leftward, from the problem description (indicating deceleration of
51. (a) The potential energy is
8.99 109 N m2 C 2 5.0 10 6 C q2 U= = 4 0 d 100 m .
= 0.225 J
relative to the potential energy at infinite separation. (b) Each sphere repels the other with a force that has magnitude
8.99 109 N m2 C 2 5.0 106 C q2
33. Consider an infinitesimal segment of the rod, located between x and x + dx. It has length dx and contains charge dq = dx = cx dx. Its distance from P1 is d + x and the potential it creates at P1 is
1 1 cx dx dq = . 4 0 d + x 4 0 d + x
To find the
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Today's Topics The Physics 202 Team Course Formality and Overview Ch. 23-I: Electric Charge, Coulomb's Law Text: Serway and Jewett,
Physics for Scientists and Engineers, 6th ed.
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