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Unformatted text preview: Department of Physics PHY 2048 Chapter 6.1 Force & Motion: Friction N s s F f = max Mg F f F s N s s ext = = = max max Coefficient of static friction s : Case 1: v = 0 & a = 0 Block f s Table F N F g F ext M Coefficient of kinetic friction k : If on object does not move ( i.e. v = 0 a = 0) then the static frictional force, f s , and the component of the external force F ext that is parallel to the surface balance each other and the maximum value of the magnitude of f s is given by If the object begins to slide along the surface ( i.e. v 0) then the magnitude of the frictional force, rapidly decreases to a value f k , where N k k F f = Case 2: v not 0 Block f Table F N F g F ext M v ) ( g a M F k ext + = and and Maximum external force without the block sliding! Note that k < s . Department of Physics PHY 2048 Chapter 6.2 Friction: Examples F ext Fig. 2 M s = tan Example (static friction): Example (kinetic friction): (Fig. 2) A block of mass M slides along the floor while (Fig....
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