phys101 hw7

# phys101 hw7 - Both balls are initially at rest Only the...

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Physics 101 2010F Homework Assignment 7 Due at start of class October 15 Name __________________________________ (Note: Each numbered question is of equal weight. You must show your work or explain your answers to get full credit, simply writing a numerical answer is not sufficient.) 1. (a) There are three charged balls, A, B, and C. Ball A is positively charged. When A is placed near B they attract. When ball B and ball C are placed close they repel. Is the charge on ball C positive or negative? (b) If you place A near C, is the force between them attractive or repulsive? (c) If you now double the distance between A and C, how does the magnitude of the force between them change? (d) Salt water contains an equal number of positive and negative ions. When salt water is flowing through a pipe, does it constitute and electric current? 2. A 1kg ball with charge +1mC is located 2m away from a 2kg ball of charge +4mC.
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Unformatted text preview: Both balls are initially at rest. Only the electric force between the balls is acting on them. (a) What is the magnitude of the force on each of the balls? (b) What is the initial acceleration of each of these balls, both the magnitude and direction? 3. (a) A lightning stroke lasts 0.025 s and involves a flow of 100 C. What is the current? (b) A current of 0.7 A goes through an electric motor for 10 min. How many Coulombs of charge flow through it during that time? 4. (a) A +2mC charge is in an electric field of 1000 N/C to the north. What is the electric force on the charge (magnitude and direction)? (b) What is the magnitude and direction of acceleration of an electron in the above electric field? 5. How much work is done on +6C of electric charge if it moves from the positive terminal to the negative terminal of a battery which as a 12V potential difference between the two terminals....
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