[CAUT] Friction (was restrung D)

[John Delacour]

At 6:11 pm -0500 16/4/07, David Porritt wrote:

>You stated "Friction <http://en.wikipedia.org/wiki/Friction> is proportional
>to (a) the coefficient of friction of the materials and (b) the normal force
>between the surfaces."Ê
>
>It is also proportional to amount of surface contact involved.

I wonder why this  belief of yours has never made it into the physics 
text books
during all the time friction and printing have been around!

>That's why racers have big tires.  It's why pushing a large sanding 
>block on wood is harder than pushing a small block.  That's why big 
>trucks have big brake pads.

Big trucks achieve greater stopping power by the application of 
greater _force_, using compressed air.  It is the increased normal 
force that results in greater friction and the parts are made big in 
order to distribute wear and spread the heat produced (which causes a 
reduction in the coefficient of friction, and thus brake fade) over a 
larger area.

>Strings burried into soft iron will have more surface contact and 
>result in more friction than a string touching only at one point.

Just as a matter of interest, where do you get cast-iron that is 
soft?!  Why, after all this time, don't they make agraffes with 
square holes or at least the bearing surface straight and not 
rounded?  In fact you will occasionally come across agraffes with a 
steel pin inserted across the top to reduce contact area.  Apart from 
the expense, the reason they did not catch on is that they are 
designed on the basis of the false principle you are putting forward.

I suggest you do some reading and get your facts straight before you 
contradict the laws of nature.

JD