On dry concrete, a car can decelerate at a rate of 7.00m/s² , whereas on wet concrete it can decelerate at only 7.00m/s². Find the distances necessary to stop a car moving at 30.0 m/s (about 110 km/h)

(a) On dry concrete and

(b) On wet concrete.

(c) Repeat both calculations, finding the displacement from the point where the driver sees a traffic light turn red, taking into account his reaction time of 0.500 s to get his foot on the brake.

Strategy
Draw a sketch.

In order to determine which equations are best to use, we need to list all of the known values and identify exactly what we need to solve for. We shall do this explicitly in the next several examples, using tables to set them off.

Transcribed Image Text:

v0 = 30.0 m/s Ax = ? adry = -7.00 m/s² awet = -5.00 m/s² Uf = 0 m/s