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Dog walking on a raft on water then suddenly halting

  1. Apr 21, 2013 #1
    1. The problem statement, all variables and given/known data
    A dog of mass 10.0kg is standing on a raft so that he is 20.0m from shore. He walks 8.00m along the raft towards shore and then halts. The raft has a mass of 40.0kg, and we can assume there is no friction between the raft and the water. How far is the dog from shore when he stops?

    2. Relevant equations
    EK=1/2 mv2

    3. The attempt at a solution
    This is a really tricky question and I'm not quite sure how to proceed. I know that when the dog halts, the raft moves forward towards the shore?
  2. jcsd
  3. Apr 21, 2013 #2


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    What's tricky about it? What external force would cause the raft to have a net movement?
  4. Apr 21, 2013 #3
    I find this question tricky because maybe I'm overthinking it.....

    I think the external force would be what the dog applies. Then suddenly stopping, transfers the energy to the raft causing it to more forward towards the shore?
  5. Apr 21, 2013 #4


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    Gold Member

    How is the dog external? What is the dog acting on that is external to the raft?
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