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Homework Help: Vectors & Force Physics

  1. May 24, 2013 #1
    1. The problem statement, all variables and given/known data
    a) Express each force as a Cartesian vector.

    b) Determine the magnitude and coordinate direction angles of the resultant force acting on the hook.

    See figured attached.

    2. Relevant equations

    3. The attempt at a solution
    First I expressed F1 and F2 into its x, y, and z components.
    F1: 300(cos 30°)[itex]\hat{}i[/itex] +0[itex]\hat{}j[/itex] -300(sin30°)[itex]\hat{}k[/itex]... this gives 260[itex]\hat{}i[/itex] +0[itex]\hat{}j[/itex] -150[itex]\hat{}k[/itex]

    F2: 500(cos 45)(sin 45) + 500(cos 45)(cos 30) - 500(sin 45)
    250[itex]\hat{}i[/itex] + 306[itex]\hat{}j[/itex] - 354[itex]\hat{}k[/itex]

    Resultant (FR) = F1 + F2: 510[itex]\hat{}i[/itex] +306[itex]\hat{}j[/itex] - 504[itex]\hat{}k[/itex]

    magnitude of resultant = √(5102+3062+(-504)2) ≈779 N

    θx= cos-1(510/779) ≈49°

    θy= cos-1(306/779) ≈67°

    θz= cos-1(504/779) ≈130°

    But this is wrong its supposed to be magnitude of resultant = 733N with angles of 53.5, 65.3, 133 respectively. I don't really know what im doing wrong. Any type of help would greatly be appreciated.

    Attached Files:

  2. jcsd
  3. May 24, 2013 #2
    Double check this: F2: 500(cos 45)(sin 45) + 500(cos 45)(cos 30) - 500(sin 45)
    Particulary 500(cos 45)(sin 45)
    Last edited: May 24, 2013
  4. May 24, 2013 #3
    oh wow, ... thanks!.... even when I was typing it I didn't catch it....
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