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Unformatted text preview: Chapter 6: Frictional Forces Two types: static – applies to stationary objects kinetic – applies to sliding (moving) objects Like the normal force, the Frictional Force is a contact force, but acts parallel to the interface of two objects y x n m g F A f Apply Newton’s 2 nd Law F y = N − mg = ma y = ∑ N = mg F x = F A − f = ma x ∑ If applied force is small, book does not move ( static ), a x =0, then f=f s Increase applied force, book still does not move Increase F A more, now book moves, a x ≠ 0 S A f F = S x S A x S A f ma f F ma f F > + = ⇒ = − There is some maximum static frictional force, f s max . Once the applied force exceeds it, the book moves f S max = μ S N • μ s is the coefficient of static friction, it is a dimensionless number, different for each surfaceobject pair (woodwood, woodmetal); also depends on surface preparation • μ s does not depend on the mass or surface area of the object • Has value: 0 < μ s < 1.5 • If no applied vertical force Magnitudes not vectors mg f S S μ = max...
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This note was uploaded on 12/10/2011 for the course PHY 1111 taught by Professor Stencil during the Fall '11 term at University of Georgia Athens.
 Fall '11
 Stencil
 Force, Friction

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