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Re: Friction (STATIC)

At 11:11 PM -0400 10/17/00, Ludwik Kowalski, you wrote about Re:
Friction (STATIC):

If F_st =mu_st * N then mu_st must increase gradually.
What is behind the increase mu_st from zero to the maximum
quoted in tables?


Instructors who endeavor to make their physics as 'complete and
consistent' as possible would be well advised to tread VERY lightly
around this 'Friction Equation'.

Some observant student will note that the vector nature of this
Equation is completely WRONG!
(an equal sign that connects force vectors which are orthogonal to
each other ! ! ! !)

If you use it as a Scalar Equation (without de-emphasizing that force
is a vector!) then you would be well advised to replace the = sign
with the (more) correct < = (less than or equal to).

I'm not sure WHAT the (less than or equal to) implies in regard to
causation ;-)

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