MasteringPhysics19b

MasteringPhysics19b - MasteringPhysics Assignment Print...

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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI... 1 of 13 12/19/2007 1:08 PM [ Print View ] PHCC 141: Physics for Scientists and Engineers I - Fall 2007 19b. First Law of Thermodynamics Due at 11:59pm on Monday, December 3, 2007 Hide Grading Details Number of answer attempts per question is: 5 You gain credit for: correctly answering a question in a Part, or correctly answering a question in a Hint. You lose credit for: exhausting all attempts or requesting the answer to a question in a Part or Hint, or incorrectly answering a question in a Part. Late submissions: reduce your score by 100% over each day late. Hints are helpful clues or simpler questions that guide you to the answer. Hints are not available for all questions. There is no penalty for leaving questions in Hints unanswered. Grading of Incorrect Answers For Multiple-Choice or True/False questions, you lose 100% / ( # of options - 1 ) credit per incorrect answer. For any other question, you lose 3% credit per incorrect answer. Internal Energy and Heat Capacity Internal Energy of Air In answering the questions in this problem, assume that the molecules in air (mainly and ) have five degrees of freedom at this temperature (three translational and two rotational). Part A What is the internal energy of one mole of air on a very hot summer day ( )? Part A.1 Establish the relation between internal energy and temperature What is the internal energy of moles of gas at temperature with a total of degrees of freedom? Express your answer in terms of , , , , and Boltzmann's constant . ANSWER: = Part A.2 Determine the temperature in kelvins To use the ideal gas law, you need to convert the temperature into kelvins. What does correspond to when expressed in kelvins? ANSWER: = 308 Express your answer numerically in joules to two significant figures. ANSWER: = 6400 Part B What is the internal energy of one mole of air on a typical winter day in Boston when the air temperature is . Express your answer numerically in joules to two significant figures. ANSWER: = 5500 Part C To put these results in perspective, determine how high one mole of air has to be lifted to gain a potential energy equal to the difference in the energies found in Part A and Part B. (Take the mass of one mole of air to be 28.9 .) Part C.1 Determine the potential energy gain from falling
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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI... 2 of 13 12/19/2007 1:08 PM What is the increase in gravitational potential energy of an object of mass 28.9 when it is lifted 1 (near the surface of the earth). Express your answer numerically in joules to three significant figures. Use 9.81 for the magnitude of the acceleration due to gravity. ANSWER: = 0.283 Express your answer numerically in meters to two significant figures.
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