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Homework Help: Launch with Chains

  1. Jun 7, 2010 #1
    I've read the FAQ and this is not homework, it is just a hard problem I can't solve.

    Conservation of energy cannot be used because inelastic collisions occur in bringing parts of the rope from zero velocity to v

    I start by setting up that the total mass at a position y is:
    [tex]M_{total}=M+\lambda\cdot y[/tex] and thus the momentum at any position is given by:

    [tex]p=(M+\lambda\cdot y)\cdot v[/tex] but I can't figure out an expression for v and using

    [tex]F=\frac{dp}{dt}[/tex] I get an differential equation I can't solve.

    Any help would be appreciated.
  2. jcsd
  3. Jun 7, 2010 #2


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    Science Advisor
    Homework Helper

    hi benf.stokes! :smile:
    No, you can use conservation of energy …

    the question asks for the maximum height, which would be in the limiting case of no energy loss. :wink:

    As for the question itself, I don't understand what position the mass and chain are in at the start. :confused:
  4. Jun 7, 2010 #3
    Hi tiny-tim. I think that conservation of energy can't be used is a part of the problem,my bad, and if you used conservation of energy wouldn't you get at most a square root and not a cubic one?
    At the start both the mass and the chain are at rest on the floor. Thanks for the reply
  5. Jun 7, 2010 #4
    i already arrived at the solution. Thanks anyway tiny-tim :smile:
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