Mechanics 1G - 2.001 - MECHANICS AND MATERIALS I Lecture #4...

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± ± 2.001 - MECHANICS AND MATERIALS I Lecture #4 9/18/2006 Prof. Carol Livermore TOPIC: FRICTION EXAMPLE: Box on floor μ s =Coefficient of Static Friction FBD Equation of equilibrium F y =0 N W N = W F x 1
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T F =0 T = F At impending motion only : F = μ s N Forwe l llubr icated , μ s 0 . 05. For very clean surfaces μ s 0 . 4 1. After it starts to move: F = μ k N μ k = Coefficient of kinetic friction. μ k s EXAMPLE: Block on an inclined plane Q: At what angle ( α ) does the block slide down the plane? FBD: 2
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± ± ± Equilibrium F x =0 F W sin α F = W sin α F y N W cos α N = W cos α So: F =tan α N When you have impending motion: F = μ s N μ s α What about where these forces act? M 0 FL 2 N a 2 2 L 2 a == t a n α 2 N 2 So:
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± ± So: L 2 a =t a n α 2 The resultant of the normal force and frictional force act directly ”below” the center of mass. EXAMPLE Q: For what range of W 0 is the block in equilibrium?
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This note was uploaded on 08/16/2009 for the course PESS A taught by Professor Prof during the Spring '09 term at Ohio University- Athens.

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Mechanics 1G - 2.001 - MECHANICS AND MATERIALS I Lecture #4...

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