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Homework Help: Velocity and acceleration vectors problem

  1. Feb 1, 2009 #1
    1. The problem statement, all variables and given/known data

    A car, initially going eastward, rounds a 90 degree curve and ends up heading southward. If the speedometer reading remains constant, what is the direction of the car's average acceleration vector? the angle is measured "CCW from east".

    2. Relevant equations

    3. The attempt at a solution
    i honestly do not know what the question is asking. what does it mean by rounding a 90 degree curve?
  2. jcsd
  3. Feb 1, 2009 #2


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    Homework Helper

    The car can't turn sharply; you must imagine it turning on a circular path - a rounded corner. Circular motion. A centripetal force is necessary to hold the car in circular motion. This force causes the car to accelerate in the direction of the force.

    The direction of the force an acceleration change as the car turns. If you just average the initial direction and the ending direction when it completes the quarter circle turn, you should have the direction you are looking for.
  4. Feb 1, 2009 #3
    wouldn't it just be 90 degrees then?
    am i not following correctly?
  5. Feb 1, 2009 #4
    is it possible for you to explain with an image?
  6. Feb 1, 2009 #5


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    Can't do an image just now. Picture the car initially going east, but just beginning to turn south. There must be a force on the car directed to the south. This force is actually exerted by the road on the car wheels. Of course the force can do no work on the car or we could have perpetual motion - so the force is perpendicular to the motion of the car.

    As the car turns a little more and is headed southeast, the force perpendicular to that is southwest.

    Finally as the car completes the turn and is going almost south, he force is to the west.

    Draw those 3 vectors and mentally average the directions. Or just take the direction half way through the turn.
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