OH-10-preview - Version PREVIEW OH-10 Bradley (191) 1 This...

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Unformatted text preview: Version PREVIEW OH-10 Bradley (191) 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This is Online Homework No. 10. It is due 06:00 AM Tuesday morning 4 November (Abu Dhabi Time), unless notified otherwise. Turntable Comes to a Stop 001 (part 1 of 2) 5.0 points The turntable of a record player rotates at a rate of 45 . 7 rev / min and takes 64 . 2 s to come to rest when switched off. Find the deceleration. Correct answer: 0 . 0745435 rad / s 2 . Explanation: Let : = 45 . 7 rev / min , t = 64 . 2 s , and f = 0 . The angular acceleration is = t = f- t =- t =- 45 . 7 rev / min 64 . 2 s 2 1 rev 1 min 60 s =- . 0745435 rad / s 2 , a deceleration of . 0745435 rad / s 2 . 002 (part 2 of 2) 5.0 points How many revolutions did it make before coming to rest? Correct answer: 24 . 4495 rev. Explanation: For a deceleration of , the angle is = t- 1 2 t 2 = (45 . 7 rev / min)(64 . 2 s) 1 min 60 sec- 1 2 (0 . 0745435 rad / s 2 ) (64 . 2 s) 2 1 rev 2 = 24 . 4495 rev . Rigid Rectangular System 02 003 (part 1 of 2) 5.0 points Four particles with masses 5 kg, 6 kg, 5 kg, and 2 kg are connected by rigid rods of neg- ligible mass as shown. Aassume the system rotates in the xy plane about the z axis (ori- gin, O ) with an angular speed of 4 rad / s. x y O 4 rad / s 9m 8 m 5 kg 6 kg 5 kg 2 kg Find the moment of inertia of the system about the z axis. Correct answer: 652 . 5 kg m 2 . Explanation: Let : m 1 = 5 kg , top left m 2 = 6 kg , bottom left m 3 = 5 kg , bottom right m 4 = 2 kg , top right w = 8 m , and h = 9 m . Each mass is a distance d = radicalBigg parenleftBig w 2 parenrightBig 2 + parenleftbigg h 2 parenrightbigg 2 = radicalbigg w 2 + h 2 4 from the axis of rotation, so I z = summationdisplay i m i r 2 i = d 2 summationdisplay i m i = w 2 + h 2 4 summationdisplay i m i Version PREVIEW OH-10 Bradley (191) 2 = (8 m) 2 + (9 m) 2 4 (18 kg) = 652 . 5 kg m 2 . 004 (part 2 of 2) 5.0 points Find the rotational energy of the system about the z axis. Correct answer: 5220 J. Explanation: Let : = 4 rad / s . The rotational energy of the system is K = 1 2 I z 2 = 1 2 (652 . 5 kg m 2 ) (4 rad / s) 2 = 5220 J . Swinging Rod 02 005 10.0 points A massless rod of length L has a mass 2 m fastened at its center and another mass m fastened at one end. On the opposite end from the mass m , the rod is hinged with a frictionless hinge. The rod is released from rest from an initial horizontal position; then it swings down....
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This note was uploaded on 02/16/2009 for the course PYHS 191 taught by Professor Curtise during the Spring '08 term at Abilene Christian University.

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OH-10-preview - Version PREVIEW OH-10 Bradley (191) 1 This...

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