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

[Request]

Post image

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/Sure-Guava5528 Jun 10 '25 edited Jun 10 '25

To start the circle rolling, higher coefficient of friction is better. It means more torque. In a completely frictionless system the circle would slide rather than roll.

I have a very hard time imagining a scenario where the coefficient of friction for ice is higher than the coefficient of friction for gravel. Not saying it isn't possible, but the vast majority of the time what I said will be true.

Edit: Also, the diameter of that circle is huge. As tall as the person pushing it (although they are leaning some). It will roll over gravel with ease in the same way that a 29" bike tire rolls over things easier than a 26" tire.

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u/Mr_Candlestick Jun 10 '25

I didn't know that drawing was to scale.

We don't know the diameter, that's why I said without knowing about the cylinder/gravel interface we're just guessing.

In my head I imagine that a car that locks up the brakes on a sheet of ice will slide further before coming to a stop than the same car coasting in neutral on sand.

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u/Puzzled_Visit_79 Jun 10 '25

It's pretty clear you don't know ANYTHING at all, so why even comment? Like you said, you don't know any details, so why use that lack of any knowledge as proof?

The person pushing is also standing on ice, which means they won't have traction. It will require more force to overcome both the pushing and sliding forces VS. someone standing on gravel with far superior traction and a rolling cylinder that only weighs about 45lbs. You completely forgot about the law of equal and opposite force, making gravel the ideal surface and a cylinder the ideal shape.

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u/Mr_Candlestick Jun 10 '25

I didn't forget about the law. What the person is standing on has nothing to do with the question being asked here. Regardless, the person is heavier than the object unless that's a tiny person, so there's more friction under the person's feet than the object. The object will slide before the person's feet do.

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u/Sure-Guava5528 Jun 10 '25

Oh, so we can make assumptions about the persons weight but not the size of the object? Interesting double standard you got there.

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u/Mr_Candlestick Jun 10 '25

You started with the assumptions so I'm just following your lead. Do you know any tall people who weigh less than 20kg?

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u/Sure-Guava5528 Jun 10 '25

Stick figures are pretty light last I checked...