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Linear motion and newtons law

  1. Feb 13, 2007 #1
    1. The problem statement, all variables and given/known data

    hi there, really dont know how to attempt this, could someone please give guidance, thanks. a crane needs a force of 3kN to lift a mass of 6 tonne. if the load is initially at rest and the maximum velocity is 5m/s, determine the time taken to lift the load. Any help would b great, been on with this for 2 days now. thanks

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 13, 2007 #2

    Kurdt

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    Lift it how far? Or is it the time taken for the crane to accelerate the load to 5m/s?
     
  4. Feb 13, 2007 #3
    im not sure, that is the question , just how i got it, i dont understand it at all
     
  5. Feb 13, 2007 #4

    Kurdt

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    Well I'd imagine you have to calculate the time it takes to reach its maximum speed. Do you know of the kinematic equations?
     
  6. Feb 13, 2007 #5
    no i am brand new to physics, do you know of a good site that coulld explain it to me? thank you for answering
     
  7. Feb 13, 2007 #6

    Kurdt

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    Ok there are a list of the kinematic equations here:

    https://www.physicsforums.com/showpost.php?p=905663&postcount=2

    What you'll need to do is find the acceleration of the mass due to the force from the crane using Newtons second law. Once you have the acceleration you can put it into on of the kinematic equations to find the time taken to accelerate to 5m/s.

    Like I say before the question isn't posed particularly well so I'm not surprised you're confused. Have a go anyway and if you need more assistance just ask.
     
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