Hello, I could use some help and explanation in working out this problem! A driv

Question

Hello,

I could use some help and explanation in working out this problem!

A driver is traveling at 72 km/hr when she see's a red light in the distance. She keeps traveling at this speed for 2 seconds, and then applies the brakes, decelerating the car to a stop at a rate of -5 m/s2.

a. convert the driver's initial speed into units of m/s.

b. calculate her total stopping distance, measured from the point where she first notices the red light.

c. calculate her total stopping time, measured from the point where she first notices the red light.

d. calculate her average speed, measured from the point where she first notices the red light to the point when her car comes to a stop.

Explanation / Answer

(a) 72km/h * 1m/s / 3.6km/h = 20 m/s

(c) total stopping time t = 2s + ?v/a = 2s + -20m/s/-5m/s

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