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Homework Help: Find the Acceleration of the Aar Going Downhill

  1. Nov 11, 2008 #1
    1. The problem statement, all variables and given/known data
    A car originally traveling at 30 m/s manages to break for 5 sec. while traveling 125 m downhill. At that point the breaks fail. After an additional 5 sec. it travels an additional 150 m down the hill. What was the acceleration of the car after the breaks failed?

    2. Relevant equations
    Vxf = Vxi + axt and solve for a,Xf - Xi = Vxit + (1/2)axt^2, or ax = (Vxf - Vxi)/t

    3. The attempt at a solution
    Well, I've tried to use all 3 equations to no avail, perhaps I'm using the wrong ones or I don't understand the question. Or maybe it wants the instantaneous acceleration at that instant (when breaks fail)? Any tips, suggestions are welcome, thanks.
  2. jcsd
  3. Nov 11, 2008 #2


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    Staff Emeritus
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    Homework Helper

    You'll need to apply those equations to two separate pieces of the car's motion, (1) with breaks on the first 5 sec and (2) with breaks off for the next 5 sec.
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