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ME 242 Lecture 13 02.20

# ME 242 Lecture 13 02.20 - ME 242 Dynamics Today's Key...

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1 ME 242 Dynamics February 20, 2009 Eric Wang Today’s Key Concepts Angular Impulse-Momentum • Angular Impulse • Angular Momentum • Systems of Particles • Conservation of Momentum M O dt t 1 t 2 = ( H O ) 2 ( H O ) 1 Newton’s 2 nd Law F = d dt ( mv ) When a body is acted upon by a non-zero net force , the net force is equal to the time rate of change of the body’s linear momentum: Start with Newton’s 2 nd Law Define: F = d dt ( mv ) r × F = r × d dt ( mv ) M O = r × F H O = r × mv M O = d dt ( H O ) Extension of 2 nd Law M O = d dt ( H O ) When a body is acted upon by a non-zero net moment , the net moment is equal to the time rate of change of the body’s angular momentum [about a given point] : Moment about point O M O = r × F F r Σ

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2 Angular Momentum about point O H O = r × mv H O = r × mv H O = r mv sin θ Direction from right hand rule (magnitude) Linear Angular F = d dt ( mv ) F dt t 1 t 2 = ( mv ) 2 ( mv ) 1 M O = d dt ( H O ) LI 1-2 = ( mv ) 2 ( mv ) 1 AI o 1-2 M O dt t 1 t 2 = ( H O ) 2 ( H O ) 1 = ( H O ) 2 ( H O ) 1 All Expressions Equal
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ME 242 Lecture 13 02.20 - ME 242 Dynamics Today's Key...

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