I was driving along at 20 m/s, trying to change a CD and not watching where I wa

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 42 m from a railroad crossing. And wouldn't you know it, a train moving at 30 m/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 0.43 s , what minimum acceleration did my car need for me to be here today writing these words?

Explanation / Answer

First we will do the calculation for the train part so-

reaching time for train to the road = S/v

t = S/v = 60/30 =2 sec

and now as per the question, that reaction time of driver = 0.43sec then-

Time for escape safely = 2-0.43 = 1.57 sec

Now calculation for safe escaping-

given-

u= 20m/s

s=42m

and t= 1.57 sec

then-

s =ut +1/2at2

42 = 20(1.57) +1/2(a)(1.57)2

a= 8.60 m/s2 (Its the min value acceleration for escape safely from train)

Thank you !!! Have fun

Please Rate High.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.