Fab
1 (6 wheels) slides at 63 degrees while PicOne only manages
20
Derek
Hall
From:
owner-micromouse@cs.rhul.ac.uk [mailto:owner-micromouse@cs.rhul.ac.uk] On
Behalf Of Rob Probin
Sent: 03 August 2010 22:02
To:
micromouse@cs.rhul.ac.uk
Subject: RE: Acceleration greater than
1g
I'm sure you all know this and IANAP (I am not a physicist)
but I thought I have a think about this...
If we assume that the spot on the tire that is stationary
against the maze board is responsible for 'sticking' to the board when
accelerating and cornering, and hence is mainly due to what is known as dry
static friction... then the rest of this might be
valid...
As far as I know, friction is a model of how the world
operates rather than a fundamental force. Since friction is a (useful)
conceptual model it doesn't appear have the clear delineation between action
using one physical property and another to create the
friction.
Also, as someone has already pointed out, the angle of
friction(the maximum angle before one of the two items will begin sliding) is
related to the coefficient of friction by the following
formula:
Where 'a' is the angle from horizontal and 'u' is the
static coefficient of friction between the objects.
(http://en.wikipedia.org/wiki/Friction#Angle_of_friction)
It would appear that limiting the coefficient of friction
between objects to 1 would also limit the angle to 45 degrees (unless my maths
is very bad). Isn't this rather an artificial limit for
friction?
All that said, is it *really* friction when a gecko or a
spider hangs off a vertical surface? That would have a coefficient of friction
of infinity! (Except on PTFE, interestingly, which geckos apparently have a
problem with, apparently due to the lack of van der Waals force/interaction -
http://web.archive.org/web/20071014063923/http://socrates.berkeley.edu/~peattiea/research_main.html)
Additionally there is some discussion it appears whether
surfaces that are glued together can be considered a friction force. However,
since this is a not a fundamental force of nature, I guess it dependent
entirely on the definition, i.e. in our case dry solid surfaces put
together.
What causes Friction I wondered.... apparently that's a
complex question:
http://www.redorbit.com/news/science/1833058/scientists_describe_how_friction_works/index.html
And it's been debated for a while:
http://depts.washington.edu/nanolab/ChemE554/Summaries%20ChemE%20554/Introduction%20Tribology.htm
For the reference, under *very* quick and hardly scientific
conditions (e.g. phone level application and one person (me) holding
everything!), I've just checked my mouse on my maze board and it slides at 32
degrees (approximately!), which would mean a coefficient of friction of about
0.62. That sounds rather terrible but I'd still be interested in other peoples
mice.
P.S. Best to do this on floor, otherwise your mouse might
slide off the board/table and end up on the floor ...
doh!
I suspect that, as some of the theory books suggest, the
coefficient of friction cannot be greater than one.
Perhaps it
becomes something else, ie not friction, if it appears to be greater than
one.
Like duct tape?
What is the coefficient called when it
becomes glue?
Andrew.
From: Alandibley@aol.com
Date: Tue, 3 Aug 2010
09:39:43 -0400
Subject: Re: Acceleration greater than 1g
To:
micromouse@cs.rhul.ac.uk
There
seems to be a hang-up in some quarters about a coefficient of friction
greater than one. There is no reason why the coefficient can not be
greater than one. So sometimes it is.
Regards
from Alan D.
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