PART C: How Long does it take you to stop after the light turns red? Express you

Question

PART C: How Long does it take you to stop after the light turns red? Express your answer to two significant figures and include the appropriate units.

Thank you, correct answer will receive bonus points.

You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.50 s and that your car brakes with constant acceleration. How far are you from the intersection when you begin to apply the brakes? Express your answer to two significant figures and include the appropriate units. What acceleration will bring you to rest right at the intersection? Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

a)
total distance covered before applying the brakes = 110-20*0.5 = 100 m

b)

acceleration needed = -v^2/2s = -20^2 /2*100 = -2 m/s^2

c)

t = v/a = 20/2 =10 s

total time = t + reaction time = 10+0.5 = 10.5 s

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