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Homework Help: Spring Mechanics homework problem

  1. Nov 24, 2004 #1
    There are N weights, each of mass M, connected as shown.
    At the moment of cutting the top spring, what will be the acceleration of the top and bottom weights?

    Thanks ahead :biggrin:
     

    Attached Files:

  2. jcsd
  3. Nov 25, 2004 #2
    anyone?
    my guess is that the one on the top will have a=ng and the one on the bottom a=0.
    is that right?
     
  4. Nov 25, 2004 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Since your attachment is not yet viewable, you'll have to describe the arrangement to get any help. What work have you done?
     
  5. Nov 25, 2004 #4
    there's a spring connected to a ceiling. a mass M is connected to it, to her another spring is connected, another mass etc' for N masses.
    ceiling
    -----
    /
    \
    /
    M
    \
    /
    \
    M
    \
    /
    \
    M

    Does this help? :smile:
     
  6. Nov 25, 2004 #5

    Doc Al

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    Staff: Mentor

    Sounds right to me. But no need to guess. Consider the forces on each mass, and the fact that the springs won't change lengths instantly.
     
  7. Nov 25, 2004 #6
    Well, that's what I got, but my physics teacher said he thinks it's a=0 for the bottom one, but that the one on top would have a<g, but he wasn't sure.
    That made me think I did something wrong...
     
  8. Nov 25, 2004 #7

    Doc Al

    User Avatar

    Staff: Mentor

    I don't see how he could think that the one on top could have an acceleration less than g. If the only force on it were gravity, a = g. But you've also got a stretched spring pulling it down, so a > g. Ask him to explain his reasoning. :smile:
     
  9. Nov 25, 2004 #8
    My thoughts exactly :approve:
    Well, I guess he wasn't paying enough attention or something...
    Thanks!
     
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