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Max height crate can be dropped before breaking

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data

    A 40kg crate is lifted by a poorly working hoist system that risks dropping the object, which breaks at forces exceeding 1000N. Find the maximum height to which the crate can be hoisted before it risks breaking if dropped.

    2. Relevant equations

    F=ma=mg
    U=mgh=(mv^2)/2
    Fd=U

    3. The attempt at a solution

    Yes, it's a bizarre question... I honestly have no idea how to approach this.

    This is all I could think of:

    Fd=mgh
    1000*d=40*9.81*h

    But isn't d equal to h? How does that work?

    I can't really seem to get anywhere with this...
     
  2. jcsd
  3. Sep 15, 2009 #2

    mgb_phys

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    Science Advisor
    Homework Helper

    You don't have enough information. It's not the rate of falling that matters - it's the rate of stopping at the bottom
     
  4. Sep 15, 2009 #3
    But would we not just assume that the crate stops instantaneously?
     
  5. Sep 15, 2009 #4

    Pengwuino

    User Avatar
    Gold Member

    The force would then be infinite. Remember, F = dp/dt. More information is needed for the problem.
     
  6. Sep 15, 2009 #5
    Ah, I understand here. Thank you. Problem solved... err not really, but the topic can be closed.
     
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