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 Originally Posted by dave75
Sorry, but I have to disagree. The magnets are not only applying forces in the normal plane. They are also applying tangential forces that far exceed the tangential forces applied by the weight of the Pre. You can see this in the demos when the Pre snaps into place. I think the matte finish is to hide scuffing because the Pre will rub on the Touchstone with fairly high forces.
 Originally Posted by dave75
You could have a completely frictionless surface and it would stay in place.
I really doubt that the original poster intended for this thread to become a physics discussion, and I apologize to all for my comments (both above and more in this post) having diverting it off topic.
Back a little closer to the original topic, I think there are probably several reasons for the matte finish. I happen to like the finish on my 755p, which seems to be a rubberized coating. If I ever get a Pre, I would be quite pleased if it had this same finish.
And back to the off-topic physics...as for the magnets applying a tangential force, to the best of my recollection, magnetic forces are attraction and repulsion. Yes, the attraction force could easily be great enough to hold the Pre onto a frictionless surface, perhaps even great enough to exceed the weight of the Pre and suspend it from the bottom of a horizontal surface. (Wasn't there a video with the Pre falling off the Touchstone onto the floor? Probably some inertial forces involved there.)
The only "tangential" magnetic force I can think of occurs if the magnet and the metal it is attracting have become misaligned so that the attraction force is not normal to the surface. This would be the case if the Pre is placed upon the Touchstone in a misaligned position and the attraction force pulls them into alignment ("snaps into place" as Dave75 described). In that case, friction works against the desired movement. Or in the case of weaker magnets and low friction, the Pre might slide down the slope of the Touchstone until there is misalignment and the tangential component of the attraction force keeps it from sliding farther. More friction helps prevent the undesired motion in that case, which was the point of my original comment. Depending on how you view this, I am either agreeing or disagreeing with Dave75.
An interesting experiment related to this second low-friction case is to place a reasonably strong magnet on a large, fairly smooth steel surface or perhaps to place a thin, low-friction material between the magnet and the steel surface. If the friction is low enough, then it is much easier to remove the magnet by sliding it over the surface to an edge than to pull it directly away. If the surface is vertical and the friction is low enough, the magnet may slide right down. This is often observed with refrigerator magnets trying to hold up a kids' artwork. Hopefully, that would never be the case with a Pre and a Touchstone.
So everyone go ahead and bash me for being off topic, for being too wordy, or for living under different laws of physics than you have observed. I will try not to post any more of this stuff. And I don't think I need any more expressions of affection from Pooh!
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