A person driving her car at 46.0 km/hr approaches an intersection just as the tr

Question

A person driving her car at 46.0 km/hr approaches an intersection just as the traffic light turns yellow (see figure below). She knows that the yellow light lasts only 1.60 s before turning to red, and she is a distance D = 28.0 m away from the near side of the intersection. If she decides to stop, how far from the intersection will she come to a stop? The intersection is W =11.0 m wide. Her car's maximum deceleration is -5.50 m/s2. Ignore the length of her car and her reaction time. Assume the beginning of the intersection the origin of your x-coordinate and take distances beyond the intersection to be positive and distances before the intersection to be negative. The car can accelerate from 46.0 km/hr to 69.0 km/hr in 6.50 s. How far from the intersection will she be when the light turns red?

Explanation / Answer

u=46*5/18 =12.77 m/s

s=ut-1/2 at^2 =12.77*1.6 -1/2 *5.5*1.6^2 =13.40

so she stops=28-13.40=14.6 before intersection.

thanks.

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