lecture 11

Lecture 11 - Lecture 11 Springs Hooke's law Work by nonconstant forces Power 1 Springs If I pull the spring to the right the spring pulls to the

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1 Lecture 11 Springs Hooke’s law Work by nonconstant forces Power
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2 Springs If I pull the spring to the right, the spring pulls to the left on me. Experiments with some springs show that F applied spring stretch so that F = –k x (Hooke’s law).
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3 ( 29 ( 29 2 i 2 f 2 spring 2 1 2 1 2 1 ˆ ˆ f f kx kx kx dx kx d W x x x x i i + - = - = - = = x x r F The work done by a spring is The work done by the external agent to stretch the spring (at constant v) is ( 29 ( 29 2 i 2 f F 2 1 2 1 ˆ ˆ f kx kx dx kx d W x x i - = + = = x x r F
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4 What is the spring constant? In equilibrium, the FBD for the mass is F sm w em y x x mg k mg kx w F F y = = - = = - = 0 0 em sm k is a measure of spring stiffness
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Example: An ideal spring has k = 20.0 N/m. What is the amount of work done (by an external agent) to stretch the spring 0.40 m from its relaxed length? ( 29 ( 29
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This note was uploaded on 07/04/2011 for the course PHYS 121 taught by Professor Staff during the Spring '11 term at ASU.

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Lecture 11 - Lecture 11 Springs Hooke's law Work by nonconstant forces Power 1 Springs If I pull the spring to the right the spring pulls to the

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