# Coeeficent Of Friction Lab

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28 October 2008 Introduction: Static and kinetic friction are forces that are a result of two surfaces in contact with each other. Static friction is the force that must be overcome to cause an object to begin moving, while kinetic friction occurs between two objects in motion relative to each other. The kinetic friction force, Ff, kinetic, is defined by Ff, kinetic = &#956;kFN, where &#956;k is the coefficient of kinetic friction and FN is the normal force acting on the object. The maximum static frictional force Ff, max static, is defined by Ff, static = &#956;sFN where &#956;s is the coefficient of static friction and FN is the normal force on the object. The maximum frictional force that must be overcome before movement is able to begin is &#956;sFN. If you apply a constant force to pull an object along a horizontal surface at a constant speed, then the frictional force opposing the motion is equal and opposite to the applied force, Fp. Therefore, Fp = Ff. The normal force is equal and opposite to the object’s weight when the object is on a horizontal surface and the applied force is horizontal. The question to be answered by performing this lab is how can the coefficient of static and kinetic friction be determined for an object on a horizontal surface? Materials: pulley, C-clamp, masking tape, wood surface, string, spring scale, 0-5 N, wood block Procedure: For the procedure of this lab, please refer to pages 136 and 137 in the physics textbook. Observations / Analysis: The following four data tables show calculations of static friction force, kinetic friction force, the angle of incline, and the coefficient of friction. Static Friction Force, Fs (N) FN (N) Trial 1 Trial 2 Trial 3 Average 3.5 N 2.5 N 2.6 N 2.5 N 2.5 N Kinetic Friction Force, Ff (N) FN (N) Trial 1 Trial 2 Trial 3 Average 3.5 N 2 N 2 N 2 N 2 N