A person driving her car at 41 km/h approaches an intersection just as the traff

Question

A person driving her car at 41 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning to red, and she is 30 m away from the near side of the intersection (Fig. 2-29). The intersection is 15 m wide. Her car's maximum deceleration is -5.6 m/s2, whereas it can accelerate from 41 km/h to 70 km/h in 8.7 s. Ignore the length of her car and her reaction time.

If she hits the brakes, how far will she travel before stopping?
If she hits the gas instead, how far will she travel before the light turns red?
Should she try to stop, or should she speed up to cross the intersection before the light turns red?

Explanation / Answer

First we need to convert 41 km /hour to m/s 41 km/hout = 11.39 m/s 70 km/hour = 19.44 m/s To find out how far she will travel if she hits the breaks vf^2 = vi^2 + 2*a*x 0^2 = 11.39^2 +2*-5.6*x x = 11.5832

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