
#1
Mar1409, 03:44 PM

P: 92

1. The problem statement, all variables and given/known data
Describe how you could use the procedure from this experiment to measure the coefficient of rolling friction between the tires of a car and the road surface for different pressures of air in the tires? Procedure = 1. Slide a mass along the surface of a lab desk and release the mass at a preselected "starting point" 2. Use a stopwatch and record time/dist taken for the mass to come to a complete stop. 2. Relevant equations 3. The attempt at a solution I really have no idea. Any hints would be nice :( 



#2
Mar1409, 04:18 PM

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#3
Mar1409, 04:29 PM

P: 92

Err, the car tires with more pressure will accelerate faster than the one's with less pressure.




#4
Mar1409, 05:07 PM

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P: 26,167

Coefficient of rolling friction question
Hi Draggu!
Assume it's the same as ordinary friction … what equation relates the stopping distance (from a particular speed) to the coefficient of friction? 



#5
Mar1409, 05:12 PM

P: 92

Well, I read the question over and over and I guess it's trying to say that if we put more/less pressure in the car, it can help measure the coefficient of friction?? If the tires have more pressure they weigh more (more air) but they also would roll faster than tires with less pressure, and less weight. But! newtons law states that Force= mass* acceleration
Or, Force of Friction = coefficient of friction * mass * gravity I just don't get it! and I have no idea what equation relates to that, tinytim. I'm just crappy at physics I guess 



#6
Mar1409, 05:19 PM

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but I don't think they're asking you to theorise about how the pressure affects it … just to measure the effect 



#7
Mar1409, 06:08 PM

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From kinematics then you can determine what each distance means wrt the slowing deceleration and isn't that then a result of your friction? 



#8
Mar1409, 06:51 PM

P: 92





#9
Mar1409, 07:06 PM

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http://www.physicsforums.com/showpos...63&postcount=2 One that yields a from distance and velocity perhaps? 



#10
Mar1409, 07:23 PM

P: 92

then the coefficient of friction will be Ff/Fn , and it will be negative, or positive? 



#11
Mar1409, 07:26 PM

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#12
Mar1409, 07:28 PM

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#13
Mar1409, 07:31 PM

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#14
Mar1409, 07:34 PM

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As to whether μ is positive or negative ... it will always be positive (and usually less than 1 ... usually). It's basically a ratio of 2 weights right?



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