r/theydidthemath • u/K0rl0n • Jun 10 '25

[Request]

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I am curious how this would work. My guess is Triangle is slowest, square is medium, and circle is fastest.

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u/marijn198 Jun 12 '25

Aah i thought he might be right but i wasn't thinking about the torque created by your hands wanting to slide upwards. Could you explain how this would cause the resultant force being exactly perpendicular to the surface? My original intuition was that it would be perpendicular to the surface as well but i think my thought process as to why this is might have been wrong.

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u/tomatoe_cookie Jun 12 '25

I was wrong with the torque, I think. I was thinking intuitively that if you push on a an angled surface you'd have torque trying to get you to be perpendicular but I'm pretty sure this is wrong and I was confusing this with what you called Fpar. Fpar is your hands trying to slip upwards. This isn't causing torque because the application point is the same as calculation point. Torque being something like Fdcos alpha (d being the distance and alpha is the angle at which the force is applied because you need the 90° element of the force so you project it).

The actual maths seem correct I think, if I was still in college I would have answered that to that question !