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Unformatted text preview: Physics 4B FIRST EXAM Chapters 23 - 25 Fall 1996 1 Name:_________________________________________ Solve the following problems in the space provided. Use the back of the page if needed. Each problem is worth 20 points. You must show your work in a logical fashion starting with the correctly applied physical principles which are on the last page. Your score will be maximized if your work is easy to follow because partial credit will be awarded. For full credit you must explain clearly what you are doing especially if your solution involves symmetry arguments or uses Gauss's Law. 1. The two charges q are each a distance a to the right and left of the origin as shown at the right. Find the magnitude and direction of the electric force on the charge -Q which is a very small distance y above the origin. Show that this force varies linearly with y. The magnitudes of the two forces can be found with Coulomb's Rule, r F e = k q 1 q 2 2 r r F 1 = F 2 = k qQ a 2 + y 2 These must be added as vectors, F x = F 2 cos - F 1 cos = 0 as might be expected from symmetry considerations....
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- Fall '09