# ass2 - Assignment 2 solutions 21.2.I DENTIFY The charge...

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Unformatted text preview: +Assignment 2 solutions 21.2.I DENTIFY : The charge that flows is the rate of charge flow times the duration of the time interval. S ET U P : The charge of one electron has magnitude 19 1.60 10 C. e- = E XECUTE : The rate of charge flow is 20,000 C/s and 4 100 s 1.00 10 s. t μ- = = 4 (20,000 C/s)(1.00 10 s) 2.00 C. Q- = = The number of electrons is 19 e 19 1.25 10 . 1.60 10 C Q n- = = E VALUATE : This is a very large amount of charge and a large number of electrons. 21.7. I DENTIFY : Apply Coulomb’s law. S ET U P : Consider the force on one of the spheres. (a) E XECUTE : 1 2 q q q = = 2 1 2 2 2 1 4 4 q q q F r r π π = = P P so 7 9 2 2 0.220 N 0.150 m 7.42 10 C (on each) (1/4 ) 8.988 10 N m /C F q r π- = = = P (b) 2 1 4 q q = 2 1 2 1 2 2 1 4 4 4 q q q F r r π π = = P P so 7 7 1 1 1 2 2 (7.42 10 C) = 3.71 10 C. 4(1/4 ) (1/4 ) F F q r r π π-- = = = P P And then 6 2 1 4 1.48 10 C. q q- = = E VALUATE : The force on one sphere is the same magnitude as the force on the other sphere, whether the sphere have equal charges or not. 21.13. I DENTIFY : Apply Coulomb’s law. The two forces on 3 q must have equal magnitudes and opposite directions. S ET U P : Like charges repel and unlike charges attract. E XECUTE : The force 2 F r that 2 q exerts on 3 q has magnitude 2 3 2 2 2 q q F k r = and is in the + x direction. 1 F r must be in the x- direction, so 1 q must be positive....
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ass2 - Assignment 2 solutions 21.2.I DENTIFY The charge...

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