I am using 0.3 as a friction coef. It is for the
sliding friction.
- Christopher Wright <chrisw@skypoint.com> wrote:
> >In my opinion, the friction forces never disappears
> from the system. They
> >are always present. Does this means that there is
> no friction when we are
> >standing on our feet?
> Think about standing vertically without moving there
> are no friction
> forces until there is an external force
> applied--then friction acts to
> resist the external force. It makes for a highly
> indeterminate
> situation--much more complicated than simply
> imagining what the normal
> force is and multiplying by a coefficient from a
> handbook.
>
> The point I was trying to make is that in many cases
> frictional restraint
> can't be maintained because the normal force varies
> from time to time and
> so the frictional restraint is overcome. There are a
> lot of situations
> which absolutely require consideration of friction,
> but even those don't
> involve a precise calculation because precise
> calculation really isn't
> possible. The best example I know of is the bolted
> joint. Preloading a
> bolt isn't possible without friction--the nut would
> simply spin right off
> the threads and drop to the ground. But the best you
> can do is guess at
> the friction coefficient between the threads, and
> you tighten the
> fastener according to someone's best guess, knowing
> that even that guess
> will have an error of about 30% if you're using a
> torque wrench.
>
> No one's saying always ignore friction--just think
> about what happens in
> the real world and make an intelligent judgement.
>
> Christopher Wright P.E. |"They couldn't hit an
> elephant at
> chrisw@skypoint.com | this distance" (last
> words of Gen.
> ___________________________| John Sedgwick,
> Spotsylvania 1864)
> http://www.skypoint.com/~chrisw
>
>
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Best Regards
(:- Itzhak Shdemati -:)
Received on Tue Apr 22 15:56:00 2003