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QTest #8-solutions

# QTest #8-solutions - A system oF two wheels fxed to each...

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Version 018/AABAC – QTest #8 – Antoniewicz – (57420) 1 This print-out should have 2 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A cylinder with moment oF inertia I 1 rotates with angular speed ω 0 about a Frictionless ver- tical axle. A second cylinder, with moment oF inertia I 2 = 2 3 I 1 , initially not rotating, drops onto the frst cylinder. Since the surFaces are rough, the two eventually reach the same an- gular speed ω . 2 3 I 1 I 2 I 1 ω 0 BeFore ω AFter Calculate the fnal angular speed ω with respect to the initial angular speed ω 0 . 1. ω = 4 7 ω 0 2. ω = 4 5 ω 0 3. ω = 3 4 ω 0 4. ω = 1 3 ω 0 5. ω = 3 5 ω 0 correct 6. ω = 2 5 ω 0 7. ω = 2 3 ω 0 8. ω = 3 7 ω 0 9. None oF these Explanation: s v L = const ±rom conservation oF angular momentum I 1 ω 0 = ( I 1 + I 2 ) ω , so ω = I 1 I 1 + I 2 ω 0 (1) = I 1 I 1 + 2 3 I 1 ω 0 = 3 5 ω 0 , since K is less than K 0 , kinetic energy is lost. 002 10.0 points

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Unformatted text preview: A system oF two wheels fxed to each other is Free to rotate about a Frictionless axis through the common center oF the wheels and per-pendicular to the page. ±our Forces are ex-erted tangentially to the rims oF the wheels, as shown below. F 2 F F F 2 R 3 What is the magnitude oF the net torque on the system about the axis? 1. τ = 0 2. τ = F R 3. τ = 14 F R 4. τ = 2 F R correct 5. τ = 5 F R Explanation: The three Forces F apply counter-clockwise torques while the other Force 2 F applies a clockwise torque, so τ = s F i R i Version 018/AABAC – QTest #8 – Antoniewicz – (57420) 2 = (-2 F ) (3 R ) + F (3 R ) + F (3 R ) + F (2 R ) = 2 F R ....
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QTest #8-solutions - A system oF two wheels fxed to each...

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