23lecture2a08 - Physics 2A Lecture 23 Mar 3 Vivek Sharma...

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Physics 2A Lecture 23: Mar 3 Vivek Sharma UCSD Physics
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Yo-Yo’s Speed: From Energy Perspective cm Yo-Yo made of string wrapped several times around a solid cylinder of mass M and radius R. Released w but do ith no i es not s nitial motion. S tretch or slip tring unwinds & rotates What is v of yo-yo after it drops height =h? Friction cause rotation but since no slipping on surface o No upward motion Hand doe f cylinder no mech. s no work on cylinder+s energy lost Use E con trin ser g vation: 2 2 2 2 2 1 1 1 3 2 2 2 4 cm cm cm v K mv MR Mv R = + = m 1 c 2 2 1 2 Conservation of Energ 3 4 0 0 v y 4 3 cm K U K Mg Mv U h gh + = = + = + + cm rot v is less than if yo-yo was just dropped since some energy went into rotational Kinetic Energy K
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