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Unformatted text preview: Physics 140: Winter 2012 Lecture #12 February 16, 2012 Dr. Dave Winn Racquetball Striking a Wall Copyright: Loren M. Winters Mt. Etna Andrew Davidhazy My Office Hours (1416 Randall Lab) Monday 1pm3pm Tuesday 1pm3pm Monday 4pm6pm (Jake or Joe) Q&A in chat room (Jake or Joe) Introduction to rotational motion • We have assumed that it doesn‟t matter where forces are applied to an object • We have treated everything like point objects: only move in translation • Real objects both translate and rotate • Real motions are combinations of translation and rotation: superposition • Like superposition of horizontal and vertical motion of projectiles… F push F f F N Rotational Kinematics • To describe rotation we need angular position, velocity, and acceleration • Define position as the angle between a reference line on the object and one fixed in space • Rigid bodies about a fixed axis of rotation = angular position = angular displacement = d /dt = angular velocity = d /dt = d 2 /dt 2 = angular acceleration Positions in rotational motion • Rotations must be measured in radian measure • 2 radians = 360 • 1 radian = 57.3 • Are these , , and vectors? • As long as the axis is fixed, they can be positive or negative only… r s = s/r +  Angular velocity always in the direction of angular displacement Usually: CCW = + Usually: CW =  Objects traveling in circles •...
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This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.
 Winter '11
 Winn
 Physics

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