Rolling friction

Principle

The Sensor-Unit Acceleration can be used to record the change in acceleration during rolling and so enable the coefficient of rolling friction to be simply determined. When a car rolls, the friction can be contributed to two main factors. The first of these is an inelastic
deformation of the wheels and the surface. Ideally hard rollers on an ideally hard surface would not be subject to any resistance (whereby it must be noted here that, for the same reason, a vehicle with such wheels would not be capable of starting to move on its own). The wheels of the experimental car are therefore very hard. The second important influence results from the frictional loss in the axle bearings, i.e. sliding friction in the roller bearings. As a good approximation, the rolling friction force FRR that a car experiences can be taken as being proportional to the normal force FN and being independent of the velocity. FRR = ?R . FN is therefore valid, whereby the proportionality constant ?R is called the coefficient of rolling friction. In this model, constant acceleration is to be expected up to just before standstill.

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