I set up a drinking bird and after thinking someone was messing around, I conducted an excruciating 24 hour study. The drinking bird rotates in a counter clockwise manner (in my area of the world). There are many variables untested but this is an initial finding. Pictured is a start and end with things positioned to show relative positions. It is a hypothesis at best and I think I know at least one thing causing the rotation. What do you think (dk extends the mic out to the forum).
Well, I don't think the drinking bird is supposed to rotate. Yours does that because the material it is made of is too light, which must probably affect as well for how long it can go on "drinking" nonsop. That is something you can easily fix if you glue the base to a piece of heavier material. I don't think the fact that it moves would have something to do with the Earth's rotation or what hemisphere you are in; it probably behaves like that due to the relationship between the mechanical force, the distribution of the weight and the surface it is on.
Thank you. I think likewise. I chalked it up to a light base but still find it interesting. Also, it will do its thing without a glass of water. That thing is a pretty awesome example of practical science/physics.
The rotation idea is from the notion of how a standard toilet flushes. Apparently, the rotation varies depending on the hemisphere/rotation.
You state that it is not supposed to rotate, and it could be a cheap model, but it works and it does rotate.
dk Yes, I was reading about that. Wikipedia provides a very good definition about what the drinking bird is ("The drinking bird is a heat engine that works at room temperature") and all the physics laws you can learn from it. And even with the direction of the water going down the drain, I was reading that it should be as you said, even though other factors like the irregularity of the surfaces can change that.
My best guess is that the torque and center of mass is what causes your bird to rotate.
There is an audiblethunk when it dips and that probably is what causes minute movement. Otherwise it is free floating and the internal liquid is pretty responsive to heat. You can just hold the bowl and the hand's body heat sends it up to the bird head quickly.
@ dk Great post. I love topics that can have the potential to lead into discussions on alcohol. :)
My interpretation of the situation is this. The alcohol based liquid in the drinking bird is subject to a number of different forces acting on it. Gravity, rotation of the earth, and magnetism are the ones I’m focusing on. The drinking bird mechanism is largely subjected to gravity and as joylitt said that movement of the entire thing is down to the relationship between the mechanical force, the distribution of the weight and the surface it is on.
If though we were to exclude those big factors, then what would be left would be effects due to earth rotation and magnetism. If the drinking bird was to be up scaled to the size of a trebuchet would the back wash of the liquid into the pendulus bulb create turbulence in the same manner as water in a toilet. If the drinking bird was then free to move at its base without any other forces acting on it, then would this turbulence effect be sufficient to apply a force great enough to move the entire structure? Theoretically I think it would, but only very small.
There is also the effect of magnetism. Everything is subject to magnetism. Seeing that the drinking bird is only a very small mechanism, then maybe the effect of turbulence is either increased or decreased due to magnetism depending where you are.
I’m opting for the weight distribution argument being the main cause of rotation.
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