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Math Help - 2 quick problems

  1. #1
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    2 quick problems

    I need some help on this problem and limit, i have no idea how to complete it.

    1. A train travels for 120 s between two stations. It accelerates for 30 s, maintains a constant velocity for 70 s, and brakes to a stop in 20 s. The velocity function v(t), with velocity measured in m/s, is defined as follows:




    Determine the total distance travelled by the train in the 120-second time interval.

    2. What is the limit of
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  2. #2
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    Quote Originally Posted by wren17 View Post
    I need some help on this problem and limit, i have no idea how to complete it.

    1. A train travels for 120 s between two stations. It accelerates for 30 s, maintains a constant velocity for 70 s, and brakes to a stop in 20 s. The velocity function v(t), with velocity measured in m/s, is defined as follows:




    Determine the total distance travelled by the train in the 120-second time interval.

    s=\int_{t=0}^{120} v(t)\; dt = \int_{t=0}^{30} v(t)\; dt + \int_{t=30}^{100} v(t)\; dt + \int_{t=100}^{120} v(t)\; dt

    and that you should be able to do.

    RonL
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    Thanks i actually just started to figure that out, im still stuck with the limit though
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  4. #4
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    Quote Originally Posted by wren17 View Post
    2. What is the limit of
    Lets assume you want the limit as x goes to zero. Well you could try either expanding the numerator as a power series about zero, or apply L'Hopital's rule (three times I think should do it).

    RonL
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  5. #5
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    Ok, thats similar to what i was attempting but each time i would get stuck rather quickly
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  6. #6
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    L'Hospital

    Yeah, the limit gives 0/0 but this is undefined. So, the limit is what's of consequence not the actual function value. That means that it's not really determinant that they go to the same limit. It's the rate at which they converge to this limit respectively that makes a difference. This is exactly what L'Hospitals rule is for. Thieving jerk (L'Hospital, not any of you.)
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    Quote Originally Posted by wkrepelin View Post
    [snip]
    This is exactly what L'Hospitals rule is for. Thieving jerk (L'Hospital, not any of you.)
    Au contraire.

    Read this: http://www.macalester.edu/aratra/edi.../Lhospital.pdf

    for the facts of the paid arrangement (contract) between l'Hospital and John Bernoulli ......
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    Quote Originally Posted by wren17 View Post
    Ok, thats similar to what i was attempting but each time i would get stuck rather quickly
    Show your work and it will be easier to help you.
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  9. #9
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    Quote Originally Posted by mr fantastic View Post
    Au contraire.

    Read this: http://www.macalester.edu/aratra/edi.../Lhospital.pdf

    for the facts of the paid arrangement (contract) between l'Hospital and John Bernoulli ......
    Now there's a coincidence, the source of the pdf is a book (together with the Lesbegue Integral sequal) sitting in my shopping trolly at Amazon waiting for me to save enough to buy it

    RonL
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  10. #10
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    Quote Originally Posted by wkrepelin View Post
    Thieving jerk (L'Hospital, not any of you.)
    Not that different an arrangement than that offered by the "We write your thesis for you" people who regularly spamm this site

    RonL
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  11. #11
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    Quote Originally Posted by CaptainBlack View Post
    Now there's a coincidence, the source of the pdf is a book (together with the Lesbegue Integral sequal) sitting in my shopping trolly at Amazon waiting for me to save enough to buy it

    RonL
    lol! Mine too, now (do you get paid a commission, Captain?)

    Getting off-topic a little bit ....... But for those interested:

    Amazon.com: A Radical Approach to Real Analysis: Second Edition (Classroom Resource Materials): David M. Bressoud: Books

    Amazon.com: A Radical Approach to Lebesgue's Theory of Integration (Mathematical Association of America Textbooks): David M Bressoud: Books
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