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Calculate acceleration of the system

  1. Dec 6, 2009 #1
    1. The problem statement, all variables and given/known data
    A 28.0 kg block is connected to an empty 1 kg bucket by a cord running over a frictionless pulley. The coefficient of static friction between the table and block is 0.320. Sand is gradually added to the bucket until the system just begins to move. a) calculate the mass of sand added to bucket. b) Calculate acceleration of the system


    2. Relevant equations
    Sum of forces=MA
    Ff=uFn

    3. The attempt at a solution
     
  2. jcsd
  3. Dec 6, 2009 #2

    Delphi51

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    Re: homework,

    You are supposed to write up your attempt - surely you have something, perhaps the diagram of forces or equations for the sum of forces = ma on each object.
     
  4. Dec 6, 2009 #3
    Re: homework,

    i really dont know how to start it, i drew a diagram but im not sure what to do next
     
  5. Dec 6, 2009 #4

    Delphi51

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    Re: homework,

    What forces act on the bucket?
    What forces act on the block?
     
  6. Dec 6, 2009 #5
    Re: homework,

    gravity and the normal force
    The normal force, gravity, friction?
     
  7. Dec 6, 2009 #6
    Re: homework,

    The bucket has gravity acting on it and the tension in the cord. The block has gravity, friction and the tension in the cord. The tensions in the cord are THE SAME.

    When the tension in the cord is equal to the force of friction ANY SECOND after this the system is going to start moving. Is there any way you can define the tension in the cord using the forces on either the bucket or the block?
     
  8. Dec 6, 2009 #7

    Delphi51

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    Re: homework,

    Great - you are started! Now use the two formulas you listed.
     
  9. Dec 6, 2009 #8
    Re: homework,

    Tension in the cord on the bucket is equal to the gravitational force?
     
  10. Dec 6, 2009 #9
    Re: homework,

    Yes, the tension in the cord is equal to the gravitational force of the bucket. Both tensions are the same.
     
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