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- The frictional force between two stationary surfaces is called the static friction, fs.
- The frictional force between two sliding surfaces is called the kinetic friction, fk.
- It can be shown empirically that between two particular surfaces
- static friction fs ranges from zero to a maximum value.
0 < fs < μsN
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- kinetic friction fk is constant and independent of speed.
fk = μkN
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- maximum static friction is larger than kinetic friction.
- Even though there are exceptions, friction (both static and kinetic) is usually not dependent on the area of contact.