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What is the net force acting on the ring?

  1. Nov 10, 2008 #1
    1. The problem statement, all variables and given/known data

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    2. Relevant equations



    3. The attempt at a solution

    I have absolutley no idea how to do this problem. Can anyone start me off?
     
  2. jcsd
  3. Nov 10, 2008 #2
    A Force is a vector. In this case the force can be written in terms of an x and y-component.

    Write down the 3 forces in terms of x and y-components.
    Once you have done that, you can calculate the net force by adding up all components in each direction.

    Final step will be to calculate the magnitude of that vector

    marlon
     
  4. Nov 11, 2008 #3
    I did ...

    Sin (30) = op/200
    Sin (30) x 200 = op = 100
    F1 = 100
    F2 = Sin(60) = op/200 x 200
    Sin (60) x 200 = op
    173.21 = op
    F2 = 173
    F3 = 224

    Total forces added up is 497.

    What did I do wrong?? Physics test in a few hours
     
  5. Nov 11, 2008 #4
    I don't understand what you are doing here. What's this op ?

    Force 1 : -200 e_x
    Force 2 : 100 e_x
    Force 3 : 200(cos30 e_x + sin30 e_y)

    e_x : components in the x-direction
    e_y : components in the y-direction

    Do you understand the 3 above equations ?
    How can you calculate the resulting net force of the 3 forces?

    marlon
     
  6. Nov 11, 2008 #5
    Force 1 : -200 e_x
    Force 2 : 100 e_x
    Force 3 : 100 e_y

    In total it is -100 e_x, 100y, but this is not right .
     
  7. Nov 11, 2008 #6

    Doc Al

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    Staff: Mentor

    OK. Forces 1 and 2 are totally in the x direction, so they have no y components.
    OK, that's the y-component of Force 3. What's the x-component?
     
  8. Nov 11, 2008 #7
    you are missing one component in force3. The 3rd force has TWO components !

    marlon
     
  9. Nov 11, 2008 #8
    F 3 is 100y and 100x
     
  10. Nov 11, 2008 #9
    no it's not

    how did you calculate this ?

    you need to calculate the x and y-component of a vector

    do you know how to do that ?

    hint : in your answer, you'll need to calculate the sine and cosine of an angle

    marlon
     
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