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Unformatted text preview: Version One – Homework 1 – Savrasov – 39819 – Mar 29, 2006 1 This printout should have 6 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Force Between Electrons 23:03, trigonometry, numeric, > 1 min, nor mal. 001 (part 1 of 1) 2 points Two electrons in an atom are separated by 1 . 5 × 10 10 m, the typical size of an atom. The Coulomb constant is 9 × 10 9 N · m 2 / C 2 . What is the force between them? Correct answer: 1 . 02679 × 10 8 N. Explanation: Let : d = 1 . 5 × 10 10 m and k e = 9 × 10 9 N · m 2 / C 2 . The force between the electrons is F = k e q 1 q 2 d 2 = k e q 2 e d 2 = 9 × 10 9 N · m 2 / C 2 1 . 5 × 10 10 m 2 × (1 . 60218 × 10 19 C) 2 = 1 . 02679 × 10 8 N . Hanging Charges 02 23:03, calculus, numeric, > 1 min, normal. 002 (part 1 of 1) 2 points Three identical point charges, each of mass 100 g and charge + q , hang from three strings, as in the figure. The acceleration of gravity is 9 . 8 m / s 2 , and the Coulomb constant is 8 . 98755 × 10 9 N · m 2 / C 2 . 9 . 8 m / s 2 1 . 5 c m 100 g + q 1 . 5 c m 100 g + q 45 ◦ 100 g + q If the lengths of the left and right strings are each 10 . 5 cm, and each forms an angle of 45 ◦ with the vertical, determine the value of q . Correct answer: 0 . 693444 μ C. Explanation: Let : θ = 45 ◦ , m = 100 g = 0 . 1 kg , L = 10 . 5 cm = 0 . 105 m , g = 9 . 8 m / s 2 , and k e = 8 . 98755 × 10 9 N · m 2 / C 2 . Newton’s 2nd law: X F = ma. Electrostatic force between point charges q 1 and q 2 separated by a distance r F = k e q 1 q 2 r 2 ....
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 Spring '10
 Dr.AndyGavrin
 Electrostatics, Correct Answer, Electric charge, kq

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