# Lab 106(2).docx - Physics Laboratory Report Lab 106(2...

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Physics Laboratory ReportLab 106(2): Static and Kinetic FrictionsI.Introduction1.1 Objectives1. To measure the static and kinetic frictional forces using a force sensor;2. To measure the coefficients of static friction and kinetic friction between surfaces;3. To analyze the forces using a Free-Body-Diagram (FBD) and experimentally verify your predictions of static and kinetic forces in the case that a friction cart is pulled up along an inclined plane that involves frictions.1.2 Theoretical BackgroundWhenever the surface of one body slides over that of another, each body exerts a frictional force ( f ) on the other, parallel to the surfaces. The direction of friction on each body is opposite to that of its motion relative to the other. Suppose that a block is at rest on a table with the gravitational force ( Fg) of the block balanced by a normal force ( F N) of which direction is opposite to that of gravitational force. The normal force is exerted on a body by a surface wherever the body is in contact with the surface of another body. You apply a force ( F app) on the block attempting to pull it to the right until the block starts sliding.In responding to this force, a frictional force ( f ) exactly balancing your applied force is directed to the left. The frictional force in this case is called the static frictional force( f s). As you increase the applied force further, a limiting point reaches where the block breaks away from the surface and starts to slide, which implies that there is a certain maximum value that the static frictional force can have. When the applied force is larger than the maximum static frictional force( f s, max), the object starts to slide and you must continue to exert a force to keep the object sliding. The force acting on the object while it is sliding is called kinetic frictional force( f k). You do not need to apply quite as much force to keep the object sliding as you needed to originally break free of static friction. Figure 1 illustrates the standard model of friction. The static frictional force ( f s) betweentwo surfaces can assume any value between zero and a maximum value( f s, max), i.e.,(1) 0 < f s< f s,max
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