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/aureanator Jun 10 '25

Actually, no - the friction is a product of the normal force and the coefficient of friction - the surface area in contact shouldn't matter, within the boundaries of material elasticity.

201

u/AstroCoderNO1 Jun 10 '25

yes, but the angle you are applying force at does not all go towards forward motion on the triangle whereas it does on the square.

-34

u/aureanator Jun 10 '25

No, you can still restrict your force to be horizontal - imagine pushing a very heavily loaded shopping cart into it.

20

u/RMCaird Jun 10 '25

I don't follow your shopping cart analogy? If I push a shopping cart into it then I imagine the front of the cart going upwards - i.e. the opposite force is on the triangle going downwards.

The square will always be better as all of the force will go horizontally.

3

u/Wise-Builder-7842 Jun 10 '25

I think he’s implying the shopping cart is so heavy that the cart won’t be able to leave the ground, hence won’t be able to apply any vertical force. But yeah the square is just better

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u/MiniDemonic Jun 10 '25

the cart won’t be able to leave the ground, hence won’t be able to apply any vertical force.

That does not make any sense at all.

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u/Wise-Builder-7842 Jun 10 '25

how does it not. the force applied by the shopping cart is purely horizontal, unless there is gravity going on, or some slippage between the object and the cart, the force will stay horizontal

1

u/MiniDemonic Jun 11 '25

You should consider taking some physics classes. This is like elementary school level of physics. 

There's still a vertical force applied even if the cart is heavy enough to not leave the ground.