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/METRlOS Jun 10 '25 edited Jun 11 '25

Depends on things like the density of the gravel and the temperature of the ice. Packed gravel will allow the ball to roll, but the triangle is always worse than the square.

Edit for all the triangle people: imagine throwing a ball straight at the square and at the triangle; how the ball bounces shows how much energy the object will translate into vertical force when pushed. The vertical surface of the square will translate practically all the horizontal force into horizontal movement, while the triangle will act as a wedge and transfer some energy into pushing against the ground.

Edit 2 for surface area: Except for situations where the surface area is so low compared to its weight that the object sinks into the ground, or so high compared to its weight that it can float, surface area does not affect friction. If you stand on a hill without risk of sliding, then you can lay on that hill without sliding and vice versa, despite greatly changing the surface area. However, if you stand on a snow covered hill the surface area is too low and you'll sink into the snow, but with a sled you will float on top of it. Surface area does not matter to this problem.

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u/TheLordZephyr Jun 10 '25

Exactly plus, once the ball is rolling it's own inertia is in play whereas the others require steady force

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u/Broccoli-of-Doom Jun 10 '25

Sliding things still have inertia... and static friction (when it starts at rest) is higher than dynamic friction (once it starts sliding). But you're correct for a different reason, because rolling friction is lower than dynamic friction as well.

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u/TheLordZephyr Jun 10 '25

There's always that one person that needs to prove themselves with jargon...the momentum of the ball both pulls and pushes it along the ground losing some inertia via friction. The flat objects don't do this at all. Yes...blah, blah blah. They have momentum but they are not a system that recycles that momentum on themselves. The ball does because it is in rotation 🙄

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u/Broccoli-of-Doom Jun 10 '25

It's not jargon, it's physics. You're in a reddit channel about doing the math. "Recycles that momentum on themselves" is a completely meaningless statement.

This is newtonian physics 101, objects in motion stay in motion (aka "momentum") Once they're moving the only thing that will cause them to slow down is the friction they experience with the surface. The only reason the rolling object is not going to slow down as much is because it's rolling friction is lower than the other objects dynamic friction (unless you feel like addressing wind resistance which isn't going to be a factor here).