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Understanding μk

  1. Jan 13, 2014 #1
    I'm currently a first year physics student and missed some nets and concepts and need help before exams. It would be a HUGE help if someone could explain it to me and how to use it to find things like Fn and a→ when mass and μk is given. Please i really could use this info and thanks.
  2. jcsd
  3. Jan 13, 2014 #2

    Simon Bridge

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    Welcome to PF;
    By ##\mu_k## do you mean the coefficient of kinetic friction?
    It's used the same way as any coefficient of friction.

    You use friction as an additional force in the free-body diagram.
    People tend to trip up on the direction (it changes if the velocity changes direction) and on the transition between kinetic and static cases.


    Hyperphysics appears to repeat an "obsolete idea" about friction re surface roughness.
    See: http://amasci.com/miscon/miscon4.html#fric
    ... does not affect the calculation though.
    Last edited: Jan 13, 2014
  4. Jan 13, 2014 #3
    yeah i was talking about it as as a coefficient of friction kinetic friction and thanks for the help!
  5. Jan 13, 2014 #4


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    I'm impressed you were able to decode that, Simon! I didn't have a clue what the OP was asking... :smile:
  6. Jan 13, 2014 #5

    Simon Bridge

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    @T_razz: no worries, do some examples and let me know if you get stuck.

    @berkeman: experience :D
    I need to edit my original reply slightly though: the coefficient is not the force. I'm sure nobody got confused...
  7. Jan 14, 2014 #6


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  8. Jan 14, 2014 #7

    Simon Bridge

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    I dunno - lets see... ummmm... I'm picking up an impression of a square or rectangle of light in front of you... also a general blockyness like an ordered cubism regularly under your hands.
    There's another in the background - it's fuzzy - associated with the letter D or C.
    Does this make any sense to you?
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