In static and kinetic friction problems, how is frictional force calculated?

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In static and kinetic friction problems, the frictional force is typically calculated using the formula that involves the coefficient of friction and the normal force acting on the object.

The formula F = Us * Fn is specifically used for static friction, where Us represents the coefficient of static friction and Fn stands for the normal force. The normal force is the perpendicular force exerted by a surface to support the weight of an object resting on it, effectively counteracting gravity. This relationship indicates that the maximum static frictional force increases with an increase in the normal force.

The reason this formula is pertinent for static friction is that it determines the threshold at which an object will begin to slide; it tells us how much frictional force can be generated before motion starts.

For kinetic friction, the formula would similarly use a different coefficient called the coefficient of kinetic friction, but the relationship between the frictional force and normal force still holds. In contrast, options that involve 'mg' mistakenly relate the weight of the object directly to the frictional force without considering the context of the normal force, which may vary depending on the scenario such as inclines or additional vertical loads. Thus, the correct formula for determining the frictional force in both static and kinetic scenarios involves the

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