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Homework Help: Assistance with physics vector problem

  1. Jan 20, 2009 #1
    1. The problem statement, all variables and given/known data

    Give the components of the velocity vector for wind blowing at 12 km/hr toward the southeast

    2. Relevant equations



    3. The attempt at a solution

    12cos(45)i - 12sin(45)j

    Isn't this right?
     
  2. jcsd
  3. Jan 20, 2009 #2
    Re: vectors

    Two observations.
    It's not clear what i and j represent. Sure, I'm about 99% certain I know what you mean, but I shouldn't have to guess.
    If you break a velocity into its components, are those components also velocities?
     
  4. Jan 20, 2009 #3
    Re: vectors

    i is the vector direction that represents the x axis and y is the vector direction that represents the y axis.

    and yes those components are also velocities
     
  5. Jan 20, 2009 #4
    Re: vectors

    Yes, I was sure you mean those directions, but it is not universally understood that i
    means east. And, the components shown in your answer are not velocities.
     
  6. Jan 20, 2009 #5
    Re: vectors

    so if it's not velocities then what is it? and how do I represent it in velocities?
     
  7. Jan 20, 2009 #6
    Re: vectors

    OK, we agree the components of a velocity should also be velocities. Your original velocity is a vector. Look at your components and ask whether they satisfy the requirements of a velocity vector.
     
  8. Jan 20, 2009 #7
    Re: vectors

    i still dont see it why its not a velocity vector
     
  9. Jan 20, 2009 #8
  10. Jan 21, 2009 #9
    Re: vectors

    We have the magnitude and the direction of a 2D vector (who cares if it happens to represent velocity?), and we want to resolve it into its x and y components. Equi has done this; what's up, TVP?
     
  11. Jan 21, 2009 #10
    Re: vectors

    Not to be too pedantic about this, but 8.48 east is not a velocity. The magnitude of such a velocity will always consist of a number (8.48) and a unit (km/hr). While you can set up a situation where the unit is either implied or else not needed, this is not the case here. The statement of question asks about a wind blowing to the SE and, in this instance, velocity has a real physical meaning as a ratio of distance to time and that requires a unit.
     
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