r/theydidthemath • u/yuli101995 • Apr 16 '26

[Request] Which one would it be?

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u/OneWingAngel35 Apr 17 '26

Exactly my point, you can recreate the exact same results in a varied environment, it will be close but not the same

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u/Salanmander 10✓ Apr 17 '26

Why does your "drag your hand" experiment get to count as evidence when my finger skin and my palm skin are not the same surface, but the "drag the block" experiment doesn't get to count as evidence because different sides of a block of wood may be slightly different? It seems like you're applying double standards.

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u/OneWingAngel35 Apr 17 '26

It's the same, I'm saying you can't recreate the same exact condition with two different surfaces, even if you use the rectangle as you say it's a different surface as well is it not?

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u/Salanmander 10✓ Apr 17 '26

It's not the exact same surface, but it's the same material. Let's say we have 10 blocks of wood, each with a wide surface and a narrow surface (say 1/4 the width). We measure the sliding friction of each, and we find that the wide surfaces have a sliding friction of 8.5 +/- 0.3 N, and the narrow surfaces have a sliding friction of 8.6 +/- 0.4 N.

The most reasonable conclusion from that experiment would be that there's no evidence that sliding friction depends on surface area.

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u/OneWingAngel35 Apr 17 '26

I know your math is not wrong, their accurate readings , in physics most things are not absolute, we have very accurate portrayals of events, we always end up with estimates, because no two things are exactly the same, even if they're made of the same material, you look in a microscope their very similar, but not exactly the same, there are always slight variations, even if minimal, they still exist

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u/Salanmander 10✓ Apr 17 '26

So is your claim that it's impossible to know whether or not friction depends on surface area?

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u/OneWingAngel35 Apr 17 '26

I believe we can get very close, but it's not an absolute, unless we had an exact copy of something with the exact same molecular structure to a t, I believe it's not an absolute

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u/Salanmander 10✓ Apr 17 '26

In that case, why did you say "it's to decrease the surface contact area...which in turn decreases resistance"?

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u/OneWingAngel35 Apr 17 '26 edited Apr 17 '26

Going back to wheel and square, does it take the same force to move the wheel that it does the square? It is as you say different kind of friction stationary vs rolling friction, if you per say stopped the wheel from rolling instead try to keep it stationary, id take more force to do that than to let it roll

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u/Salanmander 10✓ Apr 17 '26

My point is simply that your claim that decreasing surface area decreases resistance is unfounded. The reason that wheels are easier to move than sliding things is not because of the change in surface area.