A car of mass travelling at speed on a smooth, horizontal road attempts an emergency stop. The car skids in a straight line with none of its wheels able to rotate.
Calculate the stopping distance and time on a dry road where the dry friction coefficient between the tyres and the road is .
At high speed on a wet road the grip of each of the four tyres changes from dry friction to a lubricated drag equal to for each tyre, where is the drag coefficient and the instantaneous speed of the car. However, the tyres regain their dry-weather grip when the speed falls below . Calculate the stopping distance and time under these conditions.