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Torque Problem

  1. Nov 8, 2005 #1
    A 150N child and a 250N child sit at opposite ends of a 4.0m seesaw pivoted at its center. Where should the third child whose weight is 180N sit in order to balance the seesaw?

    Do you need to solve this problem or answer it where the 3rd child will be put
     
  2. jcsd
  3. Nov 8, 2005 #2

    Päällikkö

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    Please show what you've tried.
    What equation(s) do you think you're supposed to use?
     
  4. Nov 8, 2005 #3
    TORQUE = LENGTH * FWboy
    is it okay to assign clockwise and cclockwise to every number?
    clockwise
    TORQUE = 2.0m * 150N
    TORQUEboy1 = 300 N * m
    counterclockwise
    TORQUEboy2 = 2.0m * 250N
    TORQUEboy2 = 500N
    waaaa im so dumb
    what now
     
  5. Nov 8, 2005 #4

    Päällikkö

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    Total torque must equal 0 to keep the seesaw from rotating.
    You are using the correct formula, can you figure out what the "lenght"(/distance) should be for the 3rd boy for the torque to equal 0?
     
  6. Nov 8, 2005 #5
    oh

    Torqueboy1 + Torqueboy2 + Torqueboy3 = 0
    300N.m + 500 N * m + 180 N * M<-(unknown) = 0

    i know how but ive got a problem with Clockwise and C.Clockwise where can i assign them...

    plss helpp...
    thx
     
    Last edited: Nov 8, 2005
  7. Nov 8, 2005 #6

    Päällikkö

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    You should draw a diagram, and think where the seesaw will rotate if only one boy is placed on eg. the left.
    You can choose the sign (+/-) however you like, but all torque causing clockwise rotation must have the same sign and it must be opposite to the ones causing counter-clockwise rotation.

    I'm extremely confused about your markings, what are N.m, N * M, <-(unknown) ?
     
  8. Nov 8, 2005 #7
    oh its the Length of the third boy * Its Normal Force..
    weighing 180N to balance the seesaw..

    so i was just wondering if the third boy can be assigned at the CC or C rotation....?.. icant assign it as positive or negative
    helpp..

    thx again
     
  9. Nov 8, 2005 #8

    Päällikkö

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    Which way would the seesaw rotate if the 3rd boy wasnt placed there? To balance this rotation out, where should the 3rd boy be placed?
     
  10. Nov 8, 2005 #9
    hmm............................
    3rd boy should be with the boy weighing 150N because it's lighter
     
    Last edited: Nov 8, 2005
  11. Nov 8, 2005 #10

    Päällikkö

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    Yes, correct, sort of. It's not because of the lighter weight, but because of the smaller torque.
     
    Last edited: Nov 8, 2005
  12. Nov 8, 2005 #11
    yup i get it now thx :)
     
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