An engineer in a locomotive sees a car stuck
on the track at a railroad crossing in front of
the train. When the engineer first sees the
car, the locomotive is 150 m from the crossing
and its speed is 16 m/s.
If the engineer’s reaction time is 0.75 s,
what should be the magnitude of the mini-
mum deceleration to avoid an accident?
Stacey Warren - Expert brainly.com
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Ok, let's start by writing everything out:
reaction time = 0.75s
First figure out how much closer the train got in the 0.75s before the engineer started braking:
\[(0.75s)(16m/s)=12m\]Therefore, he needs to stop in \[150m-12m=138m\]
Now just use the kinematic equation:\[V_f^2=V_i^2+2ad\]Plug in values:\[(0m/s)^2=(16m/s)^2+2a(138m)\]Solving for a you should end up with a braking acceleration of 0.93m/s^2. This could be negative depending on your coordinate system.
Thank you so much!
I got it down to the basics but I didn't know which equation to use,