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Unformatted text preview: homework 01 FAUSAK, TAYLOR Due: Jan 21 2008, 4:00 am 1 Question 1, chap 22, sect 1. part 1 of 1 10 points You have 3 . 2 kg of water. One mole of water has a mass of 18 g / mol and each molecule of water contains 10 electrons since water is H 2 O. What is the total electron charge contained in this volume of water? Correct answer: 1 . 71296 10 8 C (tolerance 1 %). Explanation: Let : N A = 6 . 02214 10 23 molec / mol , q e = 1 . 6 10 19 C / electron , M = 18 g / mol = 0 . 018 kg / mol , m = 3 . 2 kg , and Z = 10 electrons / molec . The mass is proportional to the number of molecules, so for m grams in n molecules and M grams in N A molecules, m M = n N A n = m M N A . Since 10 electrons are in each molecule of water, then the total number of electrons n e in the coin is n e = Z n = Z m M N A and the total charge q for the n e electrons is q = n e q e = Z mN A q e M = (10 electrons / molec) 3 . 2 kg . 018 kg / mol (6 . 02214 10 23 molec / mol) ( 1 . 6 10 19 C / electron) = 1 . 71296 10 8 C . Question 2, chap 22, sect 1. part 1 of 1 10 points What happens to the mass of an object when it acquires a positive net charge by the transfer of electrons? 1. Increases 2. Decreases correct 3. Doesnt change 4. Cannot be determined Explanation: When an object acquires a positive charge it loses electrons, so its mass decreases. Question 3, chap 22, sect 2. part 1 of 1 10 points A particle of mass 85 g and charge 26 C is released from rest when it is 44 cm from a second particle of charge 10 C. Determine the magnitude of the initial ac celeration of the 85 g particle. Correct answer: 142 m / s 2 (tolerance 1 %). Explanation: Let : m = 85 g = 0 . 085 kg , q = 26 C = 2 . 6 10 5 C , r = 44 cm = 0 . 44 m , Q = 10 C = 1 10 5 C , and k e = 8 . 9875 10 9 N m 2 / C 2 . The force exerted on the particle is F = k e  q  Q  r 2 = m  a   a  = k e  q  Q  mr 2 = (8 . 9875 10 9 N m 2 / C 2 ) vextendsingle vextendsingle 2 . 6 10 5 C vextendsingle vextendsingle vextendsingle vextendsingle 1 10 5 C vextendsingle vextendsingle (0 . 085 kg) (0 . 44 m) 2 = 142 m / s 2 . Question 4, chap 22, sect 2. part 1 of 2 10 points homework 01 FAUSAK, TAYLOR Due: Jan 21 2008, 4:00 am 2 What can we conclude from the attrac tive nature of the force between a positively charged rod and an object? + + + F F ? 1. The object is an insulator. 2. Cannot be determined correct 3. The object is a conductor. Explanation: The attractive nature of the force will be the same whether the object is a conductor or insulator. Question 5, chap 22, sect 2. part 2 of 2 10 points What can we conclude from the attrac tive nature of the force between a positively charged rod and an object?...
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This note was uploaded on 03/30/2010 for the course CH 369 taught by Professor Kbrowning during the Spring '07 term at University of Texas at Austin.
 Spring '07
 KBrowning

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