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Friction without mass, help

  1. Mar 4, 2014 #1
    Friction without mass, help!!!

    the question is this as quoted. "A railroad flatcar is loaded with crates having a coefficient of static friction of 0.25 with the floor. if the train is moving at 48 km/h, in how short a distance can the train be stopped at a constant acceleration without causing the crates to slide?"

    As far as i can tell, i would need the mass to do this question. maybe I am missing something? this is a problem my professor wrote up so I believe it MAY be possible he forgot to give us mass, but then again I do recall doing something similar to this a while back.

    Thanks!
    -Sean
     
  2. jcsd
  3. Mar 4, 2014 #2

    Dick

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    Science Advisor
    Homework Helper

    You don't need the mass. If you don't know it just call it 'm' and work the problem from there. It will cancel from your answer.
     
  4. Mar 4, 2014 #3
    could you work the problem for me possibly?
     
  5. Mar 5, 2014 #4

    Borek

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    Staff: Mentor

    No, that's not how the forum works. Dick gave you a very good hint - now try to describe it with equations.
     
  6. Mar 5, 2014 #5

    Mark44

    Staff: Mentor

    As Borek said, that's not how it works here. The Homework Help Guidelines (in the PF rules - https://www.physicsforums.com/showthread.php?t=414380) says:
     
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