I want the answer for this question. I was driving along at 20 m/s, trying to ch

Question

I want the answer for this question.

I was driving along at 20 m/s, trying to change a CD and not watching where I was going. When I looked up, I found myself 48m from a railroad crossing. And wouldn't you know it, a train moving at 30m/s was only 60 m from the crossing. In a split second, I realized that the train was going to beat me to the crossing and that I didn't have enough distance to stop. My only hope was to accelerate enough to cross the tracks before the train arrived.


If my reaction time before starting to accelerate was 0.44s , what minimum acceleration did my car need for me to be here today writing these words?

Explanation / Answer

Time taken by train to reach the crossing = 60/30 = 2 s

The car needs to travel a distance of 48 m in 2 s

u = 20 m/s
t1 = 0.44 s
s1 = u*t1 = 8.8 m

Remaining distance s2 = 48 - 8.8 = 39.2 m
u = 20 m/s
t = 2- t1 = 1.56
s2 = ut + 1/2*at^2
Solve for a. a= 6.574 m/s2

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