Lect03 - Spring 2012 PHYS 172 Modern Mechanics Lecture 3 The Momentum Principle Read 2.1-2.6 1 TODAY •Relativity •Momentum Principle •Impulse

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Unformatted text preview: Spring 2012 PHYS 172: Modern Mechanics Lecture 3 - The Momentum Principle Read 2.1-2.6 1 TODAY •Relativity •Momentum Principle •Impulse •Net Force •Predicting Motion 2 RELATIVITY “ Physical laws work in the same way for observers in uniform motion as for observers at rest. ” avg v & (=in all inertial reference frames) The position update formula ( 29 f i avg f i r r v t t = +- & & & 3 “ Physical laws work in the same way for observers in uniform motion as for observers at rest. ” & v avg & v avg (=in all inertial reference frames) RELATIVITY The position update formula ( 29 f i avg f i r r v t t = +- & & & Note: all parameters must be measured with respect to the selected reference frame to predict motion with respect to that reference frame 4 The Momentum Principle & p = γ m & v γ = 1 1- & v c 2 An object moves in a straight line and at constant speed except to the extent that it interacts with other objects The Momentum Principle ∆ & p = & F net ∆ t Change of momentum is equal to the net force acting on an object times the duration of the interaction • Assume that F does not change during ∆ t What is “ force ” F ? • measure of interaction. • defined by the momentum principle. 2 F units: N m kg/s ≡ ⋅ (Newton) 6 Impulse The Momentum Principle ∆ & p = & F net ∆ t Definition of impulse Impulse ≡ & F net ∆ t Note: small...
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This note was uploaded on 02/12/2012 for the course PHYS 172 taught by Professor ? during the Spring '08 term at Purdue University-West Lafayette.

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Lect03 - Spring 2012 PHYS 172 Modern Mechanics Lecture 3 The Momentum Principle Read 2.1-2.6 1 TODAY •Relativity •Momentum Principle •Impulse

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