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Homework Help: Calculate the net force acting on the object

  1. Sep 23, 2016 #1
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    1. The problem statement, all variables and given/known data

    Calculate the net force acting on each object indicated in the following diagrams.
    (diagrams attached) I am working on "B"

    2. Relevant equations

    Sine Law: sin a/a = sin b/b = sin c/ c
    Cosine Law: c^2 = a^2 + b^2 -2ab*cos(c)
    3. The attempt at a solution
    C2 = (2W)2 + (17N)2 – 2(2)(17)Cos 45o

    = 4 + 289 – 48.08326112

    = 16 N
    SinB/ 17 N = Sin 45 / 16 W

    = 49o
    ∴ Net Force is 16 N (W49o N)
    I am really struggling with this component of physics.I understand I got the wrong answer for the sine law because I rounded off too early in my cosine law calculations. However I am really struggling to understand how I got the wrong answer for the direction of my resultant vector. It is supposed to be 16 N [W 40 N].
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Sep 23, 2016 #2


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    Science Advisor

    I can't see any attachment.
  4. Sep 23, 2016 #3
    Sorry. I attached the diagrams now
  5. Sep 23, 2016 #4


    Staff: Mentor

    It seems that if you componentized the vectors then added the components and then converted the resultant vector back to angle and magnitude.
  6. Sep 23, 2016 #5
    Yes. That's the method they want us to use.
  7. Sep 23, 2016 #6


    Staff: Mentor

    So show us the i, j components of the vectors then show the components of the resultant one.
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