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Average Velocity

  1. Jan 18, 2014 #1

    Qube

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    Gold Member

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

    The coordinate of an object is given as a function of time by x = 7t - 3t^2, where x is in meters and t is in seconds. Its average velocity over the interval from t = 0 to t = 2 s is?

    (1) -5 m/s (2) 5 m/s (3) 11 m/s (4) -11 m/s (5) -14.5 m/s

    2. Relevant equations

    Average velocity = change in position / change in time.

    3. The attempt at a solution

    Change in time = 2 seconds.

    Change in position:

    x(0) = 0.

    x(2) = 14 - 12 = 2.

    Change in position is 2.

    Therefore avg. velocity is 2/2 or 1m/s.

    Am I doing something wrong?
     
  2. jcsd
  3. Jan 18, 2014 #2

    TSny

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    Your work looks correct to me. 1 m/s is the right answer.

    [Edit: If the position function were x = 7t-3t3, then you would get one of the answers.]
     
    Last edited: Jan 18, 2014
  4. Jan 18, 2014 #3

    Qube

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    That's odd, since I copied and pasted this problem from an old physics exam of my prof's. I guess I'll have to see him about there being no correct answer among the choices.
     
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