HW2 - yang (ey942) oldhomework 02 Turner (56705) 1 This...

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Unformatted text preview: yang (ey942) oldhomework 02 Turner (56705) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Two identical positive charges exert a repul- sive force of 6 . 3 10 9 N when separated by a distance 4 . 3 10 10 m. Calculate the charge of each. The Coulomb constant is 8 . 98755 10 9 N m 2 / C 2 . Correct answer: 3 . 60013 10 19 C. Explanation: Let : F = 6 . 3 10 9 N , d = 4 . 3 10 10 m , and k e = 8 . 98755 10 9 N m 2 / C 2 . The electric force is F = k e q 1 q 2 d 2 d 2 F k e = q 2 q = radicalBigg d 2 F k e = radicalBigg (4 . 3 10 10 m) 2 (6 . 3 10 9 N) 8 . 98755 10 9 N m 2 / C 2 = 3 . 60013 10 19 C . 002 (part 1 of 2) 10.0 points Three charges are arranged as shown in the figure. x y 4 . 3 nC 3 . 9 m . 6 nC . 68 nC 1 . 6 m Find the magnitude of the electro- static force on the charge at the origin. The Coulomb cosnstant is 8 . 98755 10 9 N m 2 / C 2 . Correct answer: 2 . 09186 nN. Explanation: Let : ( x ,y ) = (0 m , 0 m) , q = . 6 nC , ( x 1 ,y 1 ) = (3 . 9 m , 0 m) , q 1 = 4 . 3 nC , ( x 2 ,y 2 ) = (0 m , 1 . 6 m) , and q 2 = 0 . 68 nC . x y q 1 x 1 q q 2 y 2 F The force vector F 10 (in the hatwider 10 direction, ) be- tween charge 6 10 10 C and 4 . 3 10 9 C is vector F 10 = + k e q q 1 x 2 1 ( ) = ( 8 . 98755 10 9 N m 2 / C 2 ) ( . 6 nC) (4 . 3 nC) (3 . 9 m) 2 = (1 . 52452 10 9 N) . The plus sign means the force vector F 10 is towards the positive x-axis. The force vector F 20 (in the hatwider 20 direction, + ) between charge 6 10 10 C and 6 . 8 10 10 C is vector F 20 = + k e q q 2 y 2 2 (+ ) = (8 . 98755 10 9 N m 2 / C 2 ) ( . 6 nC) (0 . 68 nC) ( 1 . 6 m) 2 = ( 1 . 43239 10 9 N) . The minus sign means the force vector F 20 is towards the negative y-axis. The magni- tude of the total force exerted on the charge yang (ey942) oldhomework 02 Turner (56705) 2 6 10 10 C is equal to bardbl vector F bardbl = radicalBig F 2 10 + F 2 20 = bracketleftBig (1 . 52452 10 9 N) 2 + ( 1 . 43239 10 9 N) 2 bracketrightBig 1 2 = 2...
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This note was uploaded on 11/21/2010 for the course PHY 56705 taught by Professor Turner during the Spring '10 term at University of Texas at Austin.

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HW2 - yang (ey942) oldhomework 02 Turner (56705) 1 This...

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