## Question

A car is moving at a certain speed. The minimum distance over which it can be stopped is *x*. If the speed of the car is doubled, what will be the minimum distance over which the car can be stopped during the same time?

### Solution

4*x*

Let *a* be the maximum retardation the brakes of the car can produce. Then . If *v* is doubled to 2*v*, then the minimum distance *x*^{*} is given by .

Thus *x*^{*} = 4*x*.

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