Suppose you are driving on the interstate at 85 mph when you see a highway patrol car parked up ahead. You apply your brakes, decelerating at a constant rate of 4 mph/sec until you're reduced your speed to 65 mph. You then maintain a constant speed of 65 mph. You pass the patrol car 15 seconds after you initially applied the brakes and are relieved that he doesn't pull out after you. How far away was the highway patrol car when you first saw it?(adsbygoogle = window.adsbygoogle || []).push({});

And it wants the answers in meters...

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This is what I tried doing so far, but to no avail.

v0=85mph => .0236 m/sec

vf=65mph => .0181 m/sec

t0=0

tf=15sec

a=-4mph/sec

Okay. I've tried this equation x-x0=(1/2)(v0+v)*t and solved for x with an answer of .31275 m, but that doesn't work. :-(

I've tried vf^2=v0^2+2*a(xf-x0) and solve for displacement, but that answer doesn't work either.

Maybe I'm interpreting the initial values wrong or something. Any insight appreciated.

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# Homework Help: Highway Patrol - Argh, looks so simple!

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