| Topic: |
Science > Physics |
| User: |
"Paul Ciszek" |
| Date: |
23 Jan 2004 08:44:13 AM |
| Object: |
Teaching Question: Coef. of Friction for tires? |
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
--
Please reply to: | "Evolution is a theory that accounts
pciszek at panix dot com | for variety, not superiority."
Autoreply has been disabled | -- Joan Pontius
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| User: "John T Lowry" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
08 May 2004 11:07:40 AM |
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For rolling on dry smooth concrete I use (Performance of Light Aircraft,
AIAA, 1999, p. 356) 0.02.
For braking (pp 400-401) on bare dry concrete, 0.55; on cold ice with
T<14F, 0.23; on wet ice, T>31F, 0.21.
--
John T Lowry, PhD
Flight Physics
5217 Old Spicewood Springs Rd, #312
Austin, Texas 78731
(512) 231-9391
jlowry100@earthlink.net
"Paul Ciszek" <nospam@nospam.com> wrote in message
news:burbvt$rdj$1@reader2.panix.com...
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
--
Please reply to: | "Evolution is a theory that accounts
pciszek at panix dot com | for variety, not superiority."
Autoreply has been disabled | -- Joan Pontius
.
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| User: "Mark Folsom" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
10 May 2004 12:53:26 AM |
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"John T Lowry" <jlowry100@earthlink.net> wrote in message
news:gB7nc.12320$V97.1990@newsread1.news.pas.earthlink.net...
For rolling on dry smooth concrete I use (Performance of Light Aircraft,
AIAA, 1999, p. 356) 0.02.
For braking (pp 400-401) on bare dry concrete, 0.55; on cold ice with
T<14F, 0.23; on wet ice, T>31F, 0.21.
--
John T Lowry, PhD
Flight Physics
5217 Old Spicewood Springs Rd, #312
Austin, Texas 78731
(512) 231-9391
jlowry100@earthlink.net
"Paul Ciszek" <nospam@nospam.com> wrote in message
news:burbvt$rdj$1@reader2.panix.com...
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
You might look at Car & Driver or Road & Track road test results. Cornering
and braking results, on dry pavement, seem to range between about 0.65g to
nearly 1.0g. That would meant that the coefficient of friction is at least
that high. A BMW 540i can stop in 168 feet from 70 mph without skidding any
tire--that implies a coefficient of friction of nearly .975. Some Porsches
stop quicker. You might have to dig a little more for values on ice, and I
would bet they are somewhat variable.
Mark Folsom
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| User: "" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
23 Jan 2004 12:34:39 PM |
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In article <burbvt$rdj$1@reader2.panix.com>, (Paul Ciszek) writes:
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
Web search turns up some useful stuff. "stopping distance ice"
If you know starting speed and stopping distance, you can infer
a coefficient of friction.
"Finding accurate test data on ice and snow stopping distances is difficult,
presumably because there are so many variables involved, but a U.S. government
agency test of five vehicles in dry and wet conditions is interesting. It took
a Pontiac Grand Am 45 metres to stop from 100 km/h on dry pavement but 58
metres in the wet - almost three car lengths longer. A Ford Expedition SUV
required 52 metres with dry pavement and 61 metres with it wet, a Toyota Camry
49 metres and 53 metres, and a Dodge Caravan 49 metres and 51 metres.
"A Goodyear test showed that in a stop on snow from 80 km/h a car equipped with
its winter tires required 70 metres to stop, while a car with summer touring
tires needed 112 metres and was still doing 49 km/h when it passed the 70 metre
mark.
So we have:
100 km/h, 45 meters, dry (Grand Am)
100 km/h, 58 meters, wet (Grand Am)
80 km/h, 70 meters, snow (snow tires)
80 km/h, 112 meters, snow (regular tires)
In the case of the regular tires on snow, there is an extra data
that could be used for a sanity check.
49 km/h, 42 meters, snow (regular tires)
Let me work one of them on the back of an envelope...
100 km/h and 45 meters. Assuming constant decelleration, that's
an average speed of 50 km/h or 50,000 meters in 3600 seconds.
That's 13.9 meters per second and we're covering 45 meters.
That makes 3.24 seconds. We lost 13.9 meters per second in
3.24 seconds.
That's 4.3 meters per second per second.
One g is 9.8 meters per second per second. 4.3 meters per second
is about 44 percent of that.
So the coefficient of friction for rubber on dry pavement is somewhere
around .44 for a Grand Am rolling/skidding to a stop.
John Briggs
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| User: "Paul Ciszek" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
24 Jan 2004 11:08:43 PM |
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In article <izL1S19bb0hj@eisner.encompasserve.org>,
<briggs@encompasserve.org> wrote:
In article <burbvt$rdj$1@reader2.panix.com>, (Paul
Ciszek) writes:
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
Web search turns up some useful stuff. "stopping distance ice"
If you know starting speed and stopping distance, you can infer
a coefficient of friction.
"Finding accurate test data on ice and snow stopping distances is difficult,
presumably because there are so many variables involved, but a U.S. government
agency test of five vehicles in dry and wet conditions is interesting. It took
a Pontiac Grand Am 45 metres to stop from 100 km/h on dry pavement but 58
metres in the wet - almost three car lengths longer. A Ford Expedition SUV
required 52 metres with dry pavement and 61 metres with it wet, a Toyota Camry
49 metres and 53 metres, and a Dodge Caravan 49 metres and 51 metres.
"A Goodyear test showed that in a stop on snow from 80 km/h a car equipped with
its winter tires required 70 metres to stop, while a car with summer touring
tires needed 112 metres and was still doing 49 km/h when it passed the 70 metre
mark.
So we have:
100 km/h, 45 meters, dry (Grand Am)
100 km/h, 58 meters, wet (Grand Am)
80 km/h, 70 meters, snow (snow tires)
80 km/h, 112 meters, snow (regular tires)
In the case of the regular tires on snow, there is an extra data
that could be used for a sanity check.
49 km/h, 42 meters, snow (regular tires)
Let me work one of them on the back of an envelope...
100 km/h and 45 meters. Assuming constant decelleration, that's
an average speed of 50 km/h or 50,000 meters in 3600 seconds.
That's 13.9 meters per second and we're covering 45 meters.
That makes 3.24 seconds. We lost 13.9 meters per second in
3.24 seconds.
That's 4.3 meters per second per second.
One g is 9.8 meters per second per second. 4.3 meters per second
is about 44 percent of that.
So the coefficient of friction for rubber on dry pavement is somewhere
around .44 for a Grand Am rolling/skidding to a stop.
Thank you very much!
--
Please reply to: | "Evolution is a theory that accounts
pciszek at panix dot com | for variety, not superiority."
Autoreply has been disabled | -- Joan Pontius
.
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| User: "Mark Folsom" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
25 Jan 2004 02:22:47 AM |
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"Paul Ciszek" <> wrote in message
news:buvj0r$9m0$1@reader2.panix.com...
In article <izL1S19bb0hj@eisner.encompasserve.org>,
<briggs@encompasserve.org> wrote:
In article <burbvt$rdj$1@reader2.panix.com>, (Paul
Ciszek) writes:
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
Web search turns up some useful stuff. "stopping distance ice"
If you know starting speed and stopping distance, you can infer
a coefficient of friction.
"Finding accurate test data on ice and snow stopping distances is
difficult,
presumably because there are so many variables involved, but a U.S.
government
agency test of five vehicles in dry and wet conditions is interesting. It
took
a Pontiac Grand Am 45 metres to stop from 100 km/h on dry pavement but 58
metres in the wet - almost three car lengths longer. A Ford Expedition
SUV
required 52 metres with dry pavement and 61 metres with it wet, a Toyota
Camry
49 metres and 53 metres, and a Dodge Caravan 49 metres and 51 metres.
"A Goodyear test showed that in a stop on snow from 80 km/h a car
equipped with
its winter tires required 70 metres to stop, while a car with summer
touring
tires needed 112 metres and was still doing 49 km/h when it passed the 70
metre
mark.
So we have:
100 km/h, 45 meters, dry (Grand Am)
100 km/h, 58 meters, wet (Grand Am)
80 km/h, 70 meters, snow (snow tires)
80 km/h, 112 meters, snow (regular tires)
In the case of the regular tires on snow, there is an extra data
that could be used for a sanity check.
49 km/h, 42 meters, snow (regular tires)
Let me work one of them on the back of an envelope...
100 km/h and 45 meters. Assuming constant decelleration, that's
an average speed of 50 km/h or 50,000 meters in 3600 seconds.
That's 13.9 meters per second and we're covering 45 meters.
That makes 3.24 seconds. We lost 13.9 meters per second in
3.24 seconds.
No, no, no, no, no!
You lost the starting speed, not the average speed. It's 27.8 m/s in 3.24
seconds ==> 8.57 m/s^2 or 0.875 g's.
That's 4.3 meters per second per second.
One g is 9.8 meters per second per second. 4.3 meters per second
is about 44 percent of that.
So the coefficient of friction for rubber on dry pavement is somewhere
around .44 for a Grand Am rolling/skidding to a stop.
Thank you very much!
Don't be too ready to accept someone's back-of-the-envelope calculations.
Mark Folsom
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| User: "Dave Baker" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
25 Jan 2004 02:59:09 AM |
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Subject: Re: Teaching Question: Coef. of Friction for tires?
From: (Paul Ciszek)
Date: 25/01/04 05:08 GMT Standard Time
Message-id: <buvj0r$9m0$1@reader2.panix.com>
In article <izL1S19bb0hj@eisner.encompasserve.org>,
<briggs@encompasserve.org> wrote:
In article <burbvt$rdj$1@reader2.panix.com>, (Paul
Ciszek) writes:
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
Web search turns up some useful stuff. "stopping distance ice"
If you know starting speed and stopping distance, you can infer
a coefficient of friction.
"Finding accurate test data on ice and snow stopping distances is difficult,
presumably because there are so many variables involved, but a U.S.
government
agency test of five vehicles in dry and wet conditions is interesting. It
took
a Pontiac Grand Am 45 metres to stop from 100 km/h on dry pavement but 58
metres in the wet - almost three car lengths longer. A Ford Expedition SUV
required 52 metres with dry pavement and 61 metres with it wet, a Toyota
Camry
49 metres and 53 metres, and a Dodge Caravan 49 metres and 51 metres.
"A Goodyear test showed that in a stop on snow from 80 km/h a car equipped
with
its winter tires required 70 metres to stop, while a car with summer touring
tires needed 112 metres and was still doing 49 km/h when it passed the 70
metre
mark.
So we have:
100 km/h, 45 meters, dry (Grand Am)
100 km/h, 58 meters, wet (Grand Am)
80 km/h, 70 meters, snow (snow tires)
80 km/h, 112 meters, snow (regular tires)
In the case of the regular tires on snow, there is an extra data
that could be used for a sanity check.
49 km/h, 42 meters, snow (regular tires)
Let me work one of them on the back of an envelope...
100 km/h and 45 meters. Assuming constant decelleration, that's
an average speed of 50 km/h or 50,000 meters in 3600 seconds.
That's 13.9 meters per second and we're covering 45 meters.
That makes 3.24 seconds. We lost 13.9 meters per second in
3.24 seconds.
That's 4.3 meters per second per second.
One g is 9.8 meters per second per second. 4.3 meters per second
is about 44 percent of that.
So the coefficient of friction for rubber on dry pavement is somewhere
around .44 for a Grand Am rolling/skidding to a stop.
Thank you very much!
If you can accept such obviously wrong calculations so easily should you really
be teaching a physics course?
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
I'm not at all sure why women like men. We're argumentative, childish,
unsociable and extremely unappealing naked. I'm quite grateful they do though.
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| User: "Paul Ciszek" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
25 Jan 2004 11:39:03 AM |
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In article <20040125035909.26379.00000783@mb-m07.aol.com>,
Dave Baker <pumaracing@aol.comma> wrote:
Thank you very much!
If you can accept such obviously wrong calculations so easily should you really
be teaching a physics course?
WIth the stopping distances, and assuming constant acceleration, I can
get the coefficients. The distances were the useful information;
I threw of a quick note of thanks. Don't worry, I shall never make
the mistake of thanking anyone one on Usenet ever again.
--
Please reply to: | "Mundus Vult Decipi"
pciszek at panix dot com | ("The world wants to be deceived")
Autoreply has been disabled | --James Branch Cabell
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| User: "Mark Folsom" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
25 Jan 2004 07:15:34 PM |
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"Paul Ciszek" <nospam@nospam.com> wrote in message
news:bv0uvn$kir$1@reader2.panix.com...
In article <20040125035909.26379.00000783@mb-m07.aol.com>,
Dave Baker <pumaracing@aol.comma> wrote:
Thank you very much!
If you can accept such obviously wrong calculations so easily should you
really
be teaching a physics course?
WIth the stopping distances, and assuming constant acceleration, I can
get the coefficients. The distances were the useful information;
I threw of a quick note of thanks. Don't worry, I shall never make
the mistake of thanking anyone one on Usenet ever again.
Want a Kleenex?
Mark Folsom
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| User: "Uncle Al" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
23 Jan 2004 12:21:48 PM |
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Paul Ciszek wrote:
I am teaching a freshman physics course at a community college,
and I would like to find some realistic values for the coefficient
of friction (both static *and* dynamic would be cool) of rubber
tires on dry pavement and on ice. Where does one find stuff
like this?
Google
tires "coefficient of friction" 3870 hits
It depends on the surface, on the rubber compounding, on the
temperature, on surface debris and contamination...
--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)
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| User: "Allan Morrison" |
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| Title: Re: Teaching Question: Coef. of Friction for tires? |
23 Jan 2004 05:11:27 PM |
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For some extra "fun" in class.
Get your students to calculate the acceleration of a "dragster" car -
they will know the time (just ask some of the car buff students)and
the distance (1/4 mile). The tire friction requirements for this to
occur will be greater than 1.0 .
How come?
ANS. 1 the drivers spin the tires (= friction heat)till the rubber is
hot so the tire rubber sticks(as in glue) to the concrete
and/or
2. the tire rubber is so soft that the rubber fits into the the
surface roughness holes of the concrete- generating higher "friction"
than just sitting on top of the concrete like a hard rubber tire.
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