Dynamic friction

Principle

The Sensor-Unit Acceleration can be used to record the change in speed during a sliding phase and so enable the coefficient of dynamic friction to be simply determined. When a body is pushed over a solid surface and is then allowed to slide freely, the speed of it quickly decreases and it comes to a rest. The force of dynamic friction FGR is responsible for this acceleration directed oppositely to the direction of movement. In the Coulomb friction model, which gives a good approximation for the movement of a body on a firm, even surface without lubrication, this force of dynamic friction is independent of the speed and proportional to the normal force FN. Therefore, FGR = ?G. FN is valid, whereby the proportionality constant ?G is called the coefficient of dynamic friction. The frictional force is always parallel to the direction of movement of the body and opposite to it. As the dynamic friction is not dependent on the speed in this model, one would expect, within the area of validity of it, a constant acceleration up to shortly before the body comes to a standstill.

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