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# Quiz6b - a The angular momentum of the platform stays...

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Physics 53 Quiz #6b Fall 2007 Name ___________________________ Recit. Section _______ Circle the correct answer: 1. [2 points] Consider a thin, stiff rod rotating about an axis through its center, which is oriented perpendicular to the rod. Four large massive beads can be slid into positions anywhere along the rod. If the angular momentum of the entire system is kept constant, in which configuration of the beads does the rod rotate the fastest? [Hint: Assume that the diameter of a bead is 1/10 of the length of the rod.] a) All four bead on one end of the rod. b) Two beads at each end. c) One bead on one side, three on the other side. d) The angular velocity is the same for all configurations. (a) (b) (c) 2. [2 points] A person initially stands at rest at the rim of a freely rotating platform. She then walks half-way toward the center of the platform and remains there. Which of the following statements is correct?

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Unformatted text preview: a) The angular momentum of the platform stays constant. b) The angular momentum of the person stays constant. c) The sum of the angular momenta of the platform and the person stays constant. d) None of the above. 3. [4 points] A solid disk of mass 2 kg and 10 cm radius rolls (without slipping) down a 30 ° incline, which is 4 m long. What is the velocity of the center of mass of the disk when it arrives at the bottom of the incline? [Hint: The moment of inertia I of a solid disk of mass M and radius R is 2 1 2 I MR = . Use g = 10 m/s 2 .] a) 5.16 m/s. b) 6.32 m/s. c) 7.30 m/s. d) 7.75 m/s. 4. [2 points] An object at rest begins to rotate with a constant angular acceleration. If this object rotates through 360º in 6.00 seconds, through what angle did it rotate in the first 3 seconds after it started rotating? a) 45º. b) 60º. c) 90º. d) 180º....
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