[jtfanclub]

Penguin, on Dec 25 2007, 10:04 PM, said:

2) Sloshing. To a good approximation, as the can rolls down the incline, the liquid will be at the bottom of the can in a relatively tranquil state. Any "sloshing" would happen from irregular movement, not from smooth acceleration down a flat incline. Any argument involving the turbulent movement of the liquid therefore seems irrelevant to me.

I think that's a myth.

There is considerable surface tension between the cola and the can (which is why if you get coke on the outside of the can it gets all slimy). If you think about a partly full can, that coke on the outside is going to follow the can to the top and fall down to the bottom, creating considerable sloshing.

If that's true, then a half full can of coke will take just as long to slide down as a sloshed can (which has a lot more free gas in it) in contrast to a full unsloshed can.

Somebody will have to test this....

[helene_t]

Penguin, on Dec 26 2007, 05:04 AM, said:

Here's what I think: The released gas causes increased pressure inside the can, causing the side to bulge out just a tiny bit further. This increased radius at the midsection causes an increase in the can's "moment of inertia." Even though the mass of the can doesn't change, this increased moment of inertia impedes rotational motion, and the can therefore rolls more slowly.

This was my first thought as well but I thought I came to the conclusion that the moment of inertia has no effect on the acceleration of the can. I may have been thinking wrongly.

The rotational energy is 1/2 I omega^2 and the translatoric energy 1/2 m omega^2 r^2, For a homogenous cylinder I is proportional to m r^2 so it seems to me that the rotational-to-translatoric energy ration is unaffected, and that this is the magnitude that determines the can's inertia. There could be something wrong with my reasoning or the clue could be that the can is not a homogenous cylinder.

[matmat]

Objects with a higher moment of inertia take longer to get rolling. same way that heavier objects take longer to get moving with pure translational motion. (under the action of the same force).

I've already been wrong about this once...

does anyone have a couple of clear bottles of soda to perform this experiment with?