A car was stopped on a corner for a red light. Once the light turned green, the

Question

A car was stopped on a corner for a red light. Once the light turned green, the driver immediately steps on the gas and drives down the block. Before reaching the end of the block, however, the traffic lights in front of him turned red. The man immediately lets off the gas, steps on the brakes, and brings the car to a stop right in front of the next intersection. If it took the car 11 seconds to travel the block, how long was it? The car can accelerate with an acceleration of a = 4.9 m / s2 , and it can de-accelerate with an acceleration of a =11m/s2.

Explanation / Answer

4.9*t=11*(11-t) so t=7.61 so s=.5*(7.6^2*4.9+11*(11-7.61)^2) [ s=.5*a*t^2] =205.1

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