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Principle of Conversation Of Energy question

  1. Jun 17, 2008 #1
    1. The problem statement, all variables and given/known data

    2 objects are connected by a light string passing over a light frictionless pulley. The 5kg object is released from rest. Using the principle of conservation of energy, (a) determine the speed of the 3kg object just as the 5kg object hits the ground

    The picture shows the 3kg object at rest connected by a string to a pulley vertically....and the 5kg object hangin from a string from the pulley with 4m height between the ground and the 5kg object.

    2. Relevant equations

    4.43m/s is answer to a

    3. The attempt at a solution

    .5mv^2 + g(mf-mi)y=.5(5)v^2 + (-9.8)(2)(4)===>

    2.5v^2= 78.4
    Last edited: Jun 17, 2008
  2. jcsd
  3. Jun 17, 2008 #2


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    Homework Helper

    When the 5kg object is released from rest, its acceleration in not g. Calculate its acceleration by drawing free body diagram. 3 kg moves up with the same acceleration. Then apply the conservation of energy for 3 kg mass to calculate its velocity.
  4. Jun 18, 2008 #3
    Draw An F.b.d.
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