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. She knows that the yellow light lasts only 1.70 s before turning to red, and she is a distance D = 30.0 m away from the near side of the intersection.

a) If she decides to stop how far from the intersection will she come to a stop?

The intersection is W = 17.0 m wide. Her car's maximum deceleration is -5.90 m/s^2. 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.

b) The car can accelerate form 46.0 km/hr to 75 km/hr in 6.20s. How far from the intersection will she be if the light turns red?

Explanation / Answer

u = 46 * 5/18

=12.78 m/s

s = ut - 1/2 at^2

= 12.78 * 1.70 - 1/2 * 5.9 * 1.7^2

= 13.20

-------------------------------------

she stops

= 30 - 13.20

= 16.8 before intersection.

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