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Homework Help: Newton's first Law

  1. Sep 17, 2005 #1
    Please ,
    Explain me this situation
    A spider is attached to two threads of equal length that make a 120o angle with each other. The spider is motionless and its mass is m=30mg.
    What is the tension in each thread?

    According to the Newton first Law, the sum of the force must be 0.

    T1+T2+Fspider=0
    since the threads are the same length and symetrical, T1=T2.

    Fspider=-3.0 *10-4N

    so I found T1=1.5 *10-4N

    I am surprised to see that the answer is 3.0 *10-4N on each thread

    please now I am confused! help
     
  2. jcsd
  3. Sep 17, 2005 #2

    Hurkyl

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    Forces are vectors...
     
  4. Sep 17, 2005 #3
    ok but how it is help me please?
     
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