2012_1061_Lecture_Ch_10

Solve the resulting equations for the unknowns 8 do a

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Unformatted text preview: y Newton’s second law for rotation 6.  Apply Newton’s second law for translation as needed 7.  Solve the resulting equations for the unknowns 8.  Do a rough estimate to see whether your answer makes sense. A Heavy Pulley A 15.0 N force represented by is applied to a cord wrapped around a pulley of mass M = 4.00 kg and radius R0 = 33.0 cm. The pulley accelerates uniformly from rest to an angular speed of 30.0 rad/s in 3.00 s. If there is a friction torque at the axle, determine the moment of inertia of the pulley. The pulley rotates about its center. Solution: •  Determine the torques –  Friction torque (clockwise) –  Torque of force FT (counterclockwise) •  Apply Newton’s second law for rotation –  The angular acceleration is found from the given info. ￿ 3.85 m.N I= = = 0.385 kg.m2 α 10.0 rad/s2 τ Pulley and a bucket Consider the previous pulley but now we have a bucket attached of weight 15.0 N hanging from the cord. Assume the cord has negligible mass and does not stretch or slip. (a) calculate the angular acceleration of the pulley and the linear acceleration of the bucket. (b) Determine the angular velocity of the pulley and the linear velocity of the bucket at t = 3.00 s if the pulley (and bucket ) starts from rest at t =0. Figure 10.23 Rotational Kinetic Energy Simlar to the definition of the translational kinetic energy we can define the rotational kinetic energy by analogy: Assume a rigid rotating body made out of many tiny particles Work done on an Object Rotating about a fixed axis •  If the work is done by a torque to rotate an object through the angle then •  The rate at which work is done or powe...
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This note was uploaded on 02/03/2014 for the course PHYSICS 1061 taught by Professor Tsankov during the Fall '09 term at Temple.

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