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MasteringPhysics10b

# MasteringPhysics10b - MasteringPhysics Assignment Print...

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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI. .. 1 of 11 12/19/2007 12:57 PM [ Print View ] PHCC 141: Physics for Scientists and Engineers I - Fall 2007 10b. Angular Dynamics Due at 11:59pm on Monday, October 29, 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. Conservation of Angular Momentum Record and Turntable Learning Goal: To understand how to use conservation of angular momentum to solve problems involving collisions of rotating bodies. Consider a turntable to be a circular disk of moment of inertia rotating at a constant angular velocity around an axis through the center and perpendicular to the plane of the disk (the disk's "primary axis of symmetry"). The axis of the disk is vertical and the disk is supported by frictionless bearings. The motor of the turntable is off, so there is no external torque being applied to the axis. Another disk (a record) is dropped onto the first such that it lands coaxially (the axes coincide). The moment of inertia of the record is . The initial angular velocity of the second disk is zero. There is friction between the two disks. After this "rotational collision," the disks will eventually rotate with the same angular velocity. Part A What is the final angular velocity, , of the two disks? Hint A.1 How to approach the problem Because there is friction between the record and turntable, you can't use energy conservation. However, since there are no net external torques acting on the system, angular momentum is conserved. Part A.2 Initial angular momentum Find the magnitude, , of the (combined) initial angular momenta of the two disks. Express in terms of , , and/or . ANSWER: = Part A.3 Final angular momentum Find the magnitude, , of the (combined) final angular momenta of the two disks. Express in terms of , , and/or . ANSWER: = Express in terms of , , and .

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MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrint?assignmentI. .. 2 of 11 12/19/2007 12:57 PM ANSWER: = Part B Because of friction, rotational kinetic energy is not conserved while the disks' surfaces slip over each other. What is the final rotational kinetic energy, , of the two spinning disks?
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MasteringPhysics10b - MasteringPhysics Assignment Print...

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