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Math Help - Parametric Equations

  1. #1
    Member Veronica1999's Avatar
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    Parametric Equations

    The parametric equations X = -2-3t and Y= 6+4t describe the position of the particle, in meters and seconds. How does the particle's position change each second?
    (-1/20 , 1/15) each minute? (-3 , 4)
    What is the speed of the particle in meters per second?( 0.09m/sec)
    Write parametric equations that describe this motion, using meters and minutes as units.

    Are my answers correct?
    I could not do the last problem. Help pls.
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  2. #2
    Junior Member bondesan's Avatar
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    I think the first answer is (-3,4) and the second is 60(-3,4) = (-180,240), recheck your calcs and then do the third question again.

    You should do a dimensional analisys: for x, [m] = -2[m] - 3\frac{[m]}{[s]}\cdot1[s]. To input t in minutes, then you should do: [m] = -2[m] - 3\frac{[m]}{[s]}\cdot\frac{60 [s]}{[min]}, so you get: x = -2-180t.
    Last edited by bondesan; July 29th 2010 at 11:11 AM. Reason: typo in hurry
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  3. #3
    MHF Contributor

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    Your problem said that the functions were given in "meters and seconds". If so, then the speed, given by the slope, is already in "meters per second". You appear to have divided by 60 which would be correct if the units were "meters and minutes".
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  4. #4
    Member Veronica1999's Avatar
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    Is the speed of the particle 5m/sec?

    For the last problem I seem to get X= -180t -2 and Y= 240t +6 for the parametric equations to desribe the motion in minutes.

    What am I misunderstanding?
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  5. #5
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    Quote Originally Posted by Veronica1999 View Post
    Is the speed of the particle 5m/sec?

    For the last problem I seem to get X= -180t -2 and Y= 240t +6 for the parametric equations to desribe the motion in minutes.

    What am I misunderstanding?
    yes ... speed = \sqrt{[x'(t)]^2+[y'(t)]^2}



    x = -2 meters - 3 meters per second * t seconds

    for t in minutes ...

    x = -2 meters - 180 meters per minute * t minutes

    so, your position functions for x any y where t is in minutes are correct.
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  6. #6
    Member Veronica1999's Avatar
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    Thank You!!!
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