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Chestermiller
#3
Nov10-12, 01:21 PM
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The direction of the static frictional force is equal in magnitude and opposite to the direction to the net force from the other applied forces. Thus, if the weight hanging over the pulley is greater than the component of the mass weight along the plane, the tangential static frictional force will be in the direction down the incline. If the weight hanging over the pulley is less than the component of the mass weight along the plane, the tangential static frictional force will be in the direction up the incline. Its magnitude will be equal to the difference of the two forces. The mass will only begin to slide if the magnitude of the static frictional force calculated in this way is greater or equal to the normal force times the coefficient of friction.