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Unformatted text preview: thwing (jrt2329) – Homework 01 – Yao – (59110) 1 This printout should have 21 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The five thousand billion freely moving elec trons in a penny repel one another. Why don’t they fly off the penny? 1. They are attracted to the five thou sand billion positively charged protons in the atomic nuclei of atoms in the penny. correct 2. They cause a jam when they try to fly away. 3. They don’t have enough speed. 4. The electrons attract each other. 5. The shell of the penny prevents the elec trons from flying. Explanation: The electrons are bound to the nuclei. 002 10.0 points Two uncharged metal balls, Z and X , stand on insulating glass rods. A third ball, carrying a positive charge, is brought near the ball X as shown in the figure. A conducting wire is then run between Z and X and then removed. Finally the third ball is removed. X Z + conducting wire When all this is finished 1. ball Z is negative and ball X is neutral. 2. balls Z and X are still uncharged. 3. ball Z is neutral and ball X is positive. 4. balls Z and X are both negative, but ball X carries more charge than ball Z . 5. ball Z is positive and ball X is negative. correct 6. balls Z and X are both negative, but ball Z carries more charge than ball X . 7. ball Z is neutral and ball X is negative. 8. balls Z and X are both positive. 9. ball Z is positive and ball X is neutral. 10. ball Z is negative and ball X is positive. Explanation: When the conducting wire is run between Z and X , some positive charge flows from X to Z under the influence of the positive charge of the third ball. Therefore, after the wire is removed, Z is charged positive and X is charged negative. 003 10.0 points A particle of mass 67 g and charge 22 μ C is released from rest when it is 38 cm from a second particle of charge − 26 μ C. Determine the magnitude of the initial ac celeration of the 67 g particle. Correct answer: 531 . 365 m / s 2 . Explanation: Let : m = 67 g , q = 22 μ C = 2 . 2 × 10 − 5 C , d = 38 cm = 0 . 38 m , Q = − 26 μ C = − 2 . 6 × 10 − 5 C , and k e = 8 . 9875 × 10 9 . The force exerted on the particle is F = k e  q 1  q 2  r 2 = ma bardbl vectora bardbl = k e bardbl vectorq bardblbardbl vector Q bardbl md 2 = k e vextendsingle vextendsingle 2 . 2 × 10 − 5 C vextendsingle vextendsingle vextendsingle vextendsingle − 2 . 6 × 10 − 5 C vextendsingle vextendsingle (0 . 067 kg) (0 . 38 m 2 ) = 531 . 365 m / s 2 . thwing (jrt2329) – Homework 01 – Yao – (59110) 2 004 10.0 points Two charges q 1 and q 2 are separated by a distance d and exert a force F on each other....
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This note was uploaded on 11/11/2009 for the course PHY 59110 taught by Professor Yao during the Spring '09 term at University of Texas.
 Spring '09
 YAO
 Physics, Work

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