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Friction vs NonFriction problem

  1. Dec 12, 2016 #1
    1. The problem statement, all variables and given/known data
    A block is being pushed off the table by a spring. Explain the path of motion of the block if there is friction and if there is no friction.

    2. Relevant equations
    N/A

    3. The attempt at a solution
    The block with friction will have a lower velocity than its non friction counterpart because of the friction between the block and table... what else should I write?
     
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  3. Dec 12, 2016 #2

    Simon Bridge

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    Are you saying that the block moves at a constant speed and direction, just slower than without friction?
    Notice that you were asked to explain the path of the motion - have you written about that?
     
  4. Dec 12, 2016 #3
    Yes, I'm looking for other differences between the two. Its the same scenario except one set has friction and the other does not.
     
  5. Dec 12, 2016 #4

    Simon Bridge

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    OK - so how does the object move when it is shoved off a table without friction? How would you describe that?
     
  6. Dec 12, 2016 #5
    It would accelerate quicker and have a higher velocity than its friction counterpart?
     
  7. Dec 13, 2016 #6
    Initially, before leaving the table, yes but after leaving the table that both will have same acceleration.
     
  8. Dec 13, 2016 #7

    Simon Bridge

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    That depends if friction/resistance from the air is neglected. Do we know the only friction is from the table?
     
  9. Dec 13, 2016 #8

    Simon Bridge

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    So the object accelerates with friction too? That also means the velocity is not constant right?
    That is something you did not mention before... write it down.
    The velocity when the object falls off the table will be slower in the friction case... what happens after the object leaves the table? Does "friction" include air resistance?

    [edit] Also - the question asks about the path that the object takes ... can you describe that when there is no friction?
     
    Last edited: Dec 13, 2016
  10. Dec 13, 2016 #9
    Objects are same so the air resistance is same , and gravity is anyhow same.
    The net force is same on both is objects after leaving the table.
    Therefore even if air resistance is there, we can say the acceleration will be same.

    That was my reasoning.
     
  11. Dec 13, 2016 #10

    Simon Bridge

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    The question asks to compare the path the objects take with and without friction ... if air resistance is to be cosidered as "friction" in this context, then the air resistance for the first case is zero.
     
  12. Dec 13, 2016 #11
    Anyhow, acceleration after leaving the table will be same for the both.
     
  13. Dec 14, 2016 #12

    vela

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    That's not necessarily true if you're considering velocity-dependent drag forces, but in this problem, the OP was probably supposed to neglect air resistance.
     
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