PHY 101 1nd Edition Lecture 23 Outline of Last Lecture I Two Conditions for Equilibrium II 8 3 Center of Gravity III 8 4 Solving Equilibrium Problems IV Axis of Rotation Outline of Current Lecture V 8 5 Torque and Angular Acceleration a Moment of Inertia VI 8 6 Rotational Kinetic Energy VII 8 7 Angular Momentum Current Lecture 8 5 Torque and Angular Acceleration Forces cause linear accelerations Torques cause angular accelerations When a rigid object is subject to a net torque 0 it undergoes angular acceleration The angular acceleration is proportional to the net torque and inversely proportional to the moment of inertia Recall Newton s 2nd law acceleration is proportional to the force and inversely proportional to the mass Moment of Inertia Moment of inertia of an object rotating around a circle of radius r o I mr2 o SI Unit kg m2 If the rotating system consists of several masses then o I miri2 The moment of inertia of a rotating object depends on the distribution of its masses and the location of its axis of rotation 8 6 Rotational Kinetic Energy These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute An object with linear speed also has certain translational KE center of gravity KE o KEt mv2 Similarly a rotating object has rotational KE o KEr I 2 When an object has both linear and angular speeds its KE is o KE KEt KEr V linear speed of the whole object R speed of the object rotating about the axis 8 7 Angular Momentum We have studied several angular quantities who have corresponding linear qualities o Displacement x o Acceleration a o Speed v o Torque force F o Moment of inertia mass I m o Kinetic Energy mv2 I 2 Angular momentum momentum o L I p mv o SI Unit kg m2 s
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