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Calculate the velocity of the transverse wave at any position

  1. Sep 17, 2009 #1
    a string of length l and mass m hangs freely from a fixed point
    calculate the velocity of the transverse wave at any position
    sol:
    mass per unit length is m/l
    let there be a point on the string at a distance x from free end
    tension at the point=wt of the string per unit length*part of the string
    =(m/l)*x*g
    and sol continues.

    my doubt is why isnt the upper part contributing to the tension?
    weight due to upper part must be pushing down the lower part.
     
  2. jcsd
  3. Sep 17, 2009 #2

    kuruman

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    Re: waves

    If I understand your question correctly, the answer is "You can't push with a string."
     
  4. Sep 18, 2009 #3
    Re: waves

    sir,
    the string here has considerable mass.let us consider the part x(as i have mentionedin prob) and l-x seperately.why isnt the weight due to upper part pushing down the lower part and contributing to tension?
    isnt it just like a block placed over another as in this case it is clear that the upper block exerts some force over the lower?
    thanks in advance.
     
  5. Sep 18, 2009 #4

    kuruman

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    Re: waves

    OK, let's consider lengths x above and L-x below. Draw a horizontal line on the string at x. The line has thickness dx and the rope at the line has mass dm = dx/L. Mass dm is in equilibrium and at rest. This means that the net force on it is zero. I know that the string of length L-x below dm exerts a force that is down because of its weight. In what direction should the string of length x above dm exert a force so that dm is at rest, down or up?
     
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