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How force works on two strings connected by a mass

  1. Apr 4, 2014 #1
    So if I slowly pull the A string first B string will tear apart... Cause the A string will expand and it will pull the mass and B string... So B string will reach its breaking weight before A... Cause B has an additional weight mg working on it..

    But if I suddenly pull the A string,it will tear apart but the B string will remain intact... I am trying to understand why this happens... I mean what is the exact mechanism here?

    Attached Files:

  2. jcsd
  3. Apr 4, 2014 #2
    Applying Newton's second law to the block we have

    Fnet = ma
    FA - FB + mg = ma
    FA - FB = m(a-g).

    If you pull it slowly, acceleration a is negligible and we get

    FA - FB = -mg < 0
    FA < FB

    FB is larger.

    But if you pull very fast than a is very large and we get

    FA - FB = m(a-g) >0

    FA > FB

    FA is larger.
  4. Apr 4, 2014 #3
    Thank you... :)
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