HW #1-solutions - nanni (arn437) HW #1 Erskine (56905) 1...

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Unformatted text preview: nanni (arn437) HW #1 Erskine (56905) 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points What can we conclude from the attractive na- ture of the force between a positively charged rod and an object? + + + F F ? 1. The object is a conductor. 2. The object is negatively charged. 3. The object is an insulator. 4. The object is positively charged. 5. Cannot be determined. correct Explanation: Because of the electric induction caused by the (positively or negatively) charged rod, there is always attractive force between the rod and the object unless the object has some net charge with the same sign of the charge of the rod, whether the object is an insulator or a conductor. 002 10.0 points 1) Two uncharged metal balls, X and Y , stand on glass rods and are touching. Y X 2) A third ball, carrying a negative charge, is brought near the first two. Y X 3) Then the first two balls are separated from each other, Y X 4) and the third ball is finally removed. Y X When this is all four steps are done, it is found out that 1. Balls X and Y are both positive. 2. Ball X is positive and ball Y is negative. 3. Balls X and Y are still uncharged. 4. Balls X and Y are both negative. 5. Ball X is negative and ball Y is positive. correct Explanation: When a negative ball is moved near a metal- lic object ( X and Y ), the negative charge will attract positive charges, causing X to have excess negative charge and Y to have excess positive charge ( X and Y are in contact, so the total net charge on X and Y should be zero). + Later, X and Y are separated, retaining their charges, so when the third ball is finally removed, X will have net negative charge and Y will have net positive charge. 003 10.0 points Two charges q 1 and q 2 are separated by a distance d and exert a force F on each other. nanni (arn437) HW #1 Erskine (56905) 2 What is the new force F , if charge 1 is increased to q 1 = 5 q 1 , charge 2 is decreased to q 2 = q 2 2 , and the distance is decreased to d = d 2 ? 1. F = 20 F 2. F = 50 F 3. F = 5 2 F 4. F = 100 F 5. F = 25 2 F 6. F = 25 4 F 7. F = 25 F 8. F = 5 F 9. F = 10 F correct 10. F = 5 4 F Explanation: F = k q 1 q 2 r 2 = k (5 q 1 ) parenleftbigg q 2 2 parenrightbigg parenleftbigg d 2 parenrightbigg 2 = 10 k q 1 q 2 d 2 = 10 F . 004 10.0 points A particle of mass 71 g and charge 47 C is released from rest when it is 63 cm from a second particle of charge 28 C. Determine the magnitude of the initial ac- celeration of the 71 g particle....
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This note was uploaded on 09/19/2011 for the course PHY 317 taught by Professor Gositz during the Fall '08 term at University of Texas at Austin.

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HW #1-solutions - nanni (arn437) HW #1 Erskine (56905) 1...

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