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Velocity and Acceleration together problem?

  1. Feb 27, 2013 #1
    A boy is running a a constant velocity of 3.0 m/s [E] and passes his father who is standing still. The father immediately starts to chase his son with a constant acceleration of 1.5m/s at the instant his that his son reachers him

    How long does it take the father to catch his son
     
  2. jcsd
  3. Feb 27, 2013 #2

    mfb

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    What did you do so far? Where did you run into problems?
     
  4. Feb 27, 2013 #3
    None so far. I do not understand this at all... How can I calculate Time if I have both velocity and acceleration?
     
  5. Feb 27, 2013 #4

    mfb

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    I don't see the problem.
    You can imagine this in real life, right? The father will reach his son at some point, and you have everything you need to determine the position of father and son for every point in time. You have to find the time where those two positions are the same.
     
  6. Feb 27, 2013 #5
    If im understanding your question correctly you can solve it like this...
    acceleration is meters per second per second or m/s^2
    since the fathers acceleration is CONSTANT after 1 second the father will be at v = 1.5 m/s
    and after 2 seconds the father will be at v = 3.0 m/s
    and after 3 seconds he will be at v = 4.5 m/s

    but the boy is moving at 3 meters per second (constant)
    so after 2 seconds he will be 6 meters away from the position he passed his father
    and after 3 seconds he will 9 meters away from the position he passed his father

    so calculate the distance his father moves at the same time intervals and I think you should get the answer.
     
  7. Feb 27, 2013 #6

    mfb

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    If you replace those timesteps by a general (real) variable t, this works.
     
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