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Understanding μk

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T_razz
#1
Jan13-14, 05:49 PM
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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.
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Simon Bridge
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Jan13-14, 05:56 PM
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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.

See:
http://hyperphysics.phy-astr.gsu.edu/hbase/frict.html

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.
T_razz
#3
Jan13-14, 06:15 PM
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yeah i was talking about it as as a coefficient of friction kinetic friction and thanks for the help!

berkeman
#4
Jan13-14, 06:20 PM
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Understanding μk

I'm impressed you were able to decode that, Simon! I didn't have a clue what the OP was asking...
Simon Bridge
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Jan13-14, 06:52 PM
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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...
sophiecentaur
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Jan14-14, 04:35 AM
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Psychic?
Simon Bridge
#7
Jan14-14, 07:47 PM
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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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