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Unformatted text preview: FRICTION FRICTION Dry Friction Dry Friction LEARNING OBJECTIVES LEARNING OBJECTIVES Be able to understand the Be able to understand the characteristics of dry friction characteristics of dry friction Be able to draw a FBD including Be able to draw a FBD including friction friction Be able to solve problems Be able to solve problems involving friction involving friction PREREQUISITE KNOWLEDGE PREREQUISITE KNOWLEDGE Units of measurement Units of measurement Trigonometry concepts Trigonometry concepts Rectangular component concepts Rectangular component concepts Equilibrium in 2D concepts Equilibrium in 2D concepts CHARACTERISTICS OF DRY FRICTION Friction is defined as a force of resistance acting between two materials which prevents or retards relative motion between the two materials. Dry friction is the friction between two dry solid bodies which are free from fluids or contaminants. Frictional forces act tangent to the contact surface in a direction opposing the relative motion or tendency for motion. For the body shown in the figure to be in equilibrium, the following must be true : F = P, N = W, and Nx = Ph. CHARACTERISTICS OF DRY FRICTION FRICTION CHARACTERISTICS The maximum friction force is attained just before the block begins to move (a situation that is called “impending motion”). Once the block begins to move, the frictional force typically drops and is given by F k = μ k N. where μ k is the coefficient of kinetic friction, U k < μ s . The value of the force is found using F s = μ s N, where μ s is called the coefficient of static friction. The value of μ s depends on the materials in contact. FRICTION FRICTION For a static problem, the maximum For a static problem, the maximum frictional force F frictional force F max max = N = N μ μ S S μ μ...
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This note was uploaded on 10/31/2010 for the course CEE CE 221 taught by Professor Baladi during the Fall '10 term at Michigan State University.
 Fall '10
 Baladi

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