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Mechanics basics CW

  1. Dec 23, 2013 #1
    1. The problem statement, all variables and given/known data
    The question in short: If the resultant force acting on the bracket is 750N along the x positive axis, what is the magnitude of F and the direction (theta)

    iZaWIYsl.jpg

    3. The attempt at a solution
    I have tried for several hours now trying to get this done. I have made a table for the components, Fx and Fy.

    Fx
    325cos(22.61) = 300.0215
    600cos(40) = 459.62

    Fy
    325sin(22.61)=124.9483
    -600sin(40) = -385.67

    Rx = 759.6415
    Ry = -260.6857


    But I dont know where to go from there. In all honesty I really don't have much idea on what to do.

    Please help me out. Thanks for your time for reading this!
     
  2. jcsd
  3. Dec 23, 2013 #2
    Is 325N making an angle 22.61 degrees with the horizontal?
     
  4. Dec 23, 2013 #3
    Oops. forgot to mention, I got 22.61degrees from the triangle on the 325N vector.
    I got it by doing:
    tan-1(5/12) = 22.6198
     
  5. Dec 23, 2013 #4
    I do not understand . What is 5 and 12 ?
     
  6. Dec 23, 2013 #5

    SteamKing

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    Science Advisor
    Homework Helper

    You need to review the definition of the tangent.
     
  7. Dec 23, 2013 #6

    How would you guys start this? I'm sorry to ask this but I'm fairly clueless. I'm pretty sure what I've said to the above post makes no sense
     
  8. Dec 23, 2013 #7
    You need to write the complete question .It is not clear from the OP what are the given parameters .Please state clearly what is given in the question and if any picture is given in the question then attach the image .
     
  9. Dec 23, 2013 #8
    Can you see the image?
     

    Attached Files:

  10. Dec 23, 2013 #9
    Okay...

    tan-1(5/12) is the angle which 325N force makes with the vertical not horizontal .

    If a force P makes an angle θ with the horizontal then what are its components in x and y directions ?
     
  11. Dec 23, 2013 #10
    Pcosθ for x component, and sin for y?
     
  12. Dec 23, 2013 #11
    Yes...horizontal component is Pcosθ and vertical component is Psinθ.

    If there are two forces P and R making angles θ and α respectively with the x axis,then the components of the resultant force ,T, in x and y direction (i.e Tx and Ty) will be

    Tx = Pcosθ+Rcosα

    Ty = Psinθ+Rsinα

    i.e we algebraically add the x components to get the x-component of the resultant force .Similarly we do for y-components.

    Does this make sense ?
     
    Last edited: Dec 24, 2013
  13. Dec 26, 2013 #12

    The only part which makes sense is where I have to add the x and y components to get the resultant of x and y. Where do I go from after I have the resultants?
     
  14. Dec 26, 2013 #13
    This does tell you about the component of the resultant force in x and y direction . What do you infer ?
     
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