Static and Kinetic Friction
The amount of friction force between two surfaces in contact depends on the type of the surfaces in contact and the amount of compression between the surfaces. Static friction is the force that is acting against your force before the object begins to move. If you exert a small push on the box, the box will not move because static friction is directly opposite to the push. If you apply a greater force than the static friction force, the friction increases to match the magnitude of your push. There is a limit to the magnitude of static friction, so eventually you may be able to apply a force larger than the maximum static force, and the box will move. The maximum static friction force is sometimes referred to as starting friction. We model static friction, F with the inequality F static force exerted by a surface on the object. The normal force is defined as the perpendicular component of the force exerted by the surface. In this case, the normal force is equal to the weight of the object. The kinetic friction force is sometimes call sliding friction. If an individual is moving an object at a constant velocity, the force they exert on the object must remain equal and opposite to the kinetic friction force, or the object will either stop moving or increase in velocity. The normal force is the perpendicular force that opposes the force of gravity.
In this experiment, the objectives were to compare the forces of kinetic and static friction, to observe how changing the normal force affected the average static and kinetic friction, and to calculate µk for the block and countertop. The purpose of this lab is to construct a relationship between frictional forces and the normal force on an object, to calculate the kinetic and static coeffients of friction for various objects and surfaces and to ultimately gain a solid understanding of static vs kinetic friction. In this lab you are given a pulley sensor...
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