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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.

    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


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