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Unformatted text preview: fierro (jmf2547) HW 05 berk (60290) 1 This printout should have 12 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A charged mass on the end of a light string is attached to a point on a uniformly charged vertical sheet of infinite extent. The acceleration of gravity is 9 . 8 m / s 2 and the permittivity of free space is 8 . 854 10 12 C 2 / N m 2 . 7 3 . 1 c m . 34 C 1 g A r e a l c h a r g e d e n s i t y . 1 2 C / m 2 Find the angle the thread makes with the vertically charge sheet. Correct answer: 13 . 2303 . Explanation: Let : g = 9 . 8 m / s 2 , = 8 . 854 10 12 C 2 / N m 2 , m = 1 g = 0 . 001 kg , = 0 . 12 C / m 2 = 1 . 2 10 7 C / m 2 , q = 0 . 34 C = 3 . 4 10 7 C , and L = 73 . 1 cm = 0 . 731 m . The length L of the string is superfluous. Let the tension in the string be denoted by T . The electric field due to the infinite sheet is constant in the xdirection and is vector E = 2 . In the and directions, force equilibrium tells us T sin = q 2 T cos = m g tan = T sin T cos = q 2 m g = arctan parenleftbigg q 2 m g parenrightbigg = arctan bracketleftbigg (3 . 4 10 7 C) (1 . 2 10 7 C / m 2 ) 2 (0 . 001 kg) (9 . 8 m / s 2 ) bracketrightbigg = 13 . 2303 . 002 (part 2 of 2) 10.0 points What value would in order for he angle 79 ? Correct answer: 2 . 62582 C / m 2 . Explanation: From the previous part, we know = 2 m g tan q = 2 (0 . 001 kg) ( 9 . 8 m / s 2 ) tan(79 ) 3 . 4 10 7 C (8 . 854 10 12 C 2 / N m 2 ) 10 6 C 1 C = 2 . 62582 C / m 2 . 003 10.0 points A net positive charge Q is placed on a large, thin conducting plate of are A . In electrostatic equilibrium the charge den sity on each surface and the electric field E outside the plate are 1. = Q A , E = 2. = Q 2 A , E = correct 3. = Q 2 A , E = 0 4. = 0 , E = 5. = Q 2 A , E = 2 fierro (jmf2547) HW 05 berk (60290) 2 Explanation: 004 10.0 points A nonconducting plate with infinite dimen sions carries a uniform surface charge density of 4 . 38 C / cm 2 ....
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 Spring '08
 Turner
 Charge, Mass, Light

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