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Math Help - Help please with this Homework.

  1. #1
    telinalga
    Guest

    Help please with this Homework.

    I am totally stuck on this.

    my friend asked for help on this is from her chemistry homework.

    please help me to help her:


    745g * cm / (sec2) = ____ lbs * ft / (min2)


    i would he 10000000000x times thankfull with you al..

    im new on the forum

    THanks in advance
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  2. #2
    MHF Contributor
    Joined
    Apr 2005
    Posts
    1,631
    Quote Originally Posted by telinalga View Post
    I am totally stuck on this.

    my friend asked for help on this is from her chemistry homework.

    please help me to help her:


    745g * cm / (sec2) = ____ lbs * ft / (min2)


    i would he 10000000000x times thankfull with you al..

    im new on the forum

    THanks in advance
    Welcome to the Forum!

    You know conversion factors?
    They are easy.

    1 m = 100 cm -------------a fact.
    There are, or we can make two conversion factors out of that fact.
    One is 1m/100cm.
    The other is just the reciprocal of that, 100cm/1m

    Conversion factors are used to convert one unit of value or measure to another unit of value or measure.
    The conversion factor is always to be multiplied. And it is such that the unit of the thing to be converted will be cancelled out by the conversion factor. Meaning, if the unit in the thing to be converted is in the numerator, then that unit must be in the denominator of the conversion factor.
    Also, if the unit in the thing to be converted is in the denominator, then that unit must be in the numerator of the conversion factor. The conversion factor always "fight" or "take the opposite position" so that it can eliminate or cancel the unit to be converted.
    That is why in a fact, there are always two conversion factors, which are reciprocals of each other.

    Words!

    Example. What is 234.5 cm in meters?
    The thing to be converted is cm. Into m.
    So,
    234.5cm *(1m/100cm)
    See. The cm is in the numerator of 234.5 cm. That's why of the two conversion factors of 1m = 100cm, the (1m/100cm) is used or multiplied---because the cm is in the denominator there.

    To continue,
    (234.5cm)*(1m/100cm) ----the cm's cancel each other,
    = (234.5/100) m
    = 2.345 m.
    Easy.

    -------------------------------
    745g * cm / (sec2) = ____ lbs * ft / (min2)

    745 g*cm/(sec^2) = _____lbs*ft/(min^2)

    So, convert g to lbs; cm to ft; and sec^2 to min^2.

    The conversion facts applicable are:
    1kg = 2.2 lbs, or 1000g = 2.2lbs. --------(i)

    2.54cm = 1inch,
    or (12*2.54 =) 30.48cm = 1ft. ----------(ii)

    1min = 60sec --------------------------(iii)

    Hence,
    745 g*cm/(sec^2)
    = [745g*cm/(sec^2)](2.2lbs/1000g)(1ft/30.48cm)((60sec)^2 / (1m)^2)
    The g's, cm's, and sec^2 's cancel each other,
    = (745)(2.2/1000)(1/30.48)(3600/1) lbs*ft/(min*2)
    = (745* 2.2 *1 *3600) / (1000 *30.48 *1) lbs*ft/(min^2)
    = 193.58 lbs*ft/(min^2) ------------answer.
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