The force, Frr, required to overcome rolling resistance of a car may be represen

Question

The force, Frr, required to overcome rolling resistance of a car may be represented as:-

Frr=Crr Mcar

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Where Mcar is the mass of the vehicle [kg] and Crr is the coefficient of rolling resistance [m/s2]. The rolling resistance includes the effects of friction losses in the wheel bearings, shaking and vibration of both the roadbed and the vehicle and friction of the wheels on the road.

A 4x4 MPV with a mass of 1200kg, has a coefficient of rolling resistance, Crr=0.009 m/s2. The car is being driven at 80 km/hr on a level road. If air resistance is ignored, the MPV will roll a distance of    (          ?             ) km before coming to a stop, after the gearbox is placed in neutral.

Explanation / Answer

constant resistance = 0.009*1200=10.8 N

so deceleration = FOrce /masss= 10.8/1200

distance taken to stop = initial velociyt ^2/2a = (80*5/18)^2 / 2*(10.8/1200) = 27.4 km

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