Problems 30 through 32 explore the relation between the speed of an auto and the distance it skids when the brakes are applied.

The skid marks made by an automobile indicated that its brakes were fully applied for a distance of 75 m before it came to a stop. The car in question is known to have a constant deceleration of 20 m/s² under these conditions How fast—in km/h—was the car traveling when the brakes were first applied?