what was the correct answer w Course Dast × w Course Das\" × Homepage , Online E
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what was the correct answer
w Course Dast × w Course Das" × Homepage , Online Etym × CHEM345:1 × Secure https://wwww.chegg.com E AppsPLC 207 Carmila F17/S18 Lecture Ne W Top Hat R PHYSICS 207001-SP CHEM 345 (11 unree: Du lingo ijs Mail-esme HW2-F17- Google Chrome é secure https://session.masteringphysics.com/myct/itemView?assignmentProblemID=90677778&offsetsprev; Part A 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 44 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 anough to cross the tracks before the If my reaction time before starting to accelerate was 0.46 s, what minimum acceleration did my car need for me to be here today writing these words? Express your answer to two significant figures and include the appropriate units. Re train arrived. 18.83 Submit Incorrect Try Again; 23 attempts remaining: no points deducted Provide Feedback Next> Gl 1:58 PM 0 Type here to search 2/3/2018 2Explanation / Answer
The train has 60m to go @ 30 m/s
The car has 44m to go @ 20m/s
when you react after 0.46 s, both the car and the train have moved further:
the train has 46.2 m to go @ 30 m/s
the car has 34.8 m to go @ 22 m/s
This gives the car 1.54s to make it over the crossing (train distance/train speed).
Now we know that distance
s= v0*t + 1/2*a*t*t
s = 34.8 m
v0 = 22 m/s
t = 1.54 s
this gives us
a= 2*[s/(t*t)-v0/t]
a= 2*[34.8/2.3716 - 22/1.54]
a=0.776 m/s
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