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Determine the units of the quantity described

  1. Sep 26, 2010 #1
    1. The problem statement, all variables and given/known data
    Determine the units of the quantity described by each of the following combinations of units:
    a. kg (m/s) (1/s)
    b. (kg/s) (m/s²)
    c. (kg/s) (m/s)²
    d. (kg/s) (m/s)

    2. Relevant equations

    3. The attempt at a solution
    I would attempt to solve the problem, but I don't even know what's being asked of me. I think I have reading comprehension problems :uhh: I'm not asking you to do my hw, but I'd appreciate it if you a) dumbed down the question for me b) told me how to solve it. I'm assuming you probably don't get basic questions like this often... sorry. Thanks!
    Last edited: Sep 26, 2010
  2. jcsd
  3. Sep 26, 2010 #2
    Re: txtbk - ch1s3 review - 1 problem - completely lost

    This is called dimensional analysis.
    For example, A Newton, the unit of force, is defined as the net force required to accelerate a 1kg mass with an acceleration of 1m/s2. So N = kg*m/s2
    With some algebra, you should be able to simplify the dimensions and end up with other units that are defined in terms of those units.
  4. Sep 26, 2010 #3

    Doc Al

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    Staff: Mentor

    Re: txtbk - ch1s3 review - 1 problem - completely lost

    Several of those combinations of standard units have special names. Try figuring out what kind of quantity each is, then you might be able to come up with the name. (At least I think that's what they want.)
  5. Sep 26, 2010 #4


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    Gold Member

    For part (a),
    [tex]1\frac{kg\cdot m}{s^{2}}=1N (newton)[/tex]

    The SI system has 7 base units and the rest are derived. The question is giving you a combination of bas units (kg, m, s) and asking you to give the derived units based on those. Check out this wiki: http://en.wikipedia.org/wiki/SI_derived_unit

    I think with that you can figure out the rest!
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