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Unformatted text preview: PHY6938 Proficiency Exam Spring 2002 April 5 , 2002 Mechanics 1. As shown in the diagram, two blocks with masses M 1 and M 2 are attached by an unstretchable rope around a frictionless pulley with radius r and moment of inertia I . There is no slipping between the rope and the pulley. The coefficient of kinetic friction between the blocks is the same as between block 1 and the surface, μ . A horizontal force F is applied to M 1 . Find the acceleration of M 1 . M1 M2 F I First draw a freebody diagram for M 1 , M 2 , and the pulley, being careful to label all the forces and find the line along which they act. Firstly let’s examine M 2 . It has a tension due to the string, gravity, a frictional force due its motion relative to M 1 , which we can assume is to the left, and the normal force which M 1 exerts on it to stop it from moving vertically. m 2 N m 2 2 T 2 f 2 g Note that the tension T 2 in the top half of the string does not have to equal that in the bottom half if we cannot ignore the pulley’s moment of inertia and it is accelerating. Now do the same for M 2 . Note that the two forces on M 1 due to M 2 are prescribed by m 1 m 1 f 1 F N N g 1 2 f 2 T 1 Newton’s third law to be equal and opposite to those on M 2 due to M 1 . Finally, we have the freebody diagram for the pulley We can now write down the equations of T T 2 1 I motion for these three objects. In the past we have written independent coordinates and written down constraint equations which we have formally added to our system...
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This note was uploaded on 03/11/2012 for the course PHY 3900 taught by Professor Staff during the Fall '1 term at FSU.
 Fall '1
 staff
 Friction, Inertia, Mass

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