Why isn’t a drinking bird perpetual motion?

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Why isn’t a drinking bird perpetual motion?

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18 Answers

Anonymous 0 Comments

Ultimately, it’ll stop dipping when the water in the glass evaporates below the level it can reach. The dipping bird extracts thermal energy from the water in the glass to drive its motion.

Anonymous 0 Comments

Because it is powered by water evaporating from its head and cooling it, creating a temperature difference, which in turn creates the pressure differences that make the liquid cycle up and down. Once the water source is depleted, the motion stops.

Anonymous 0 Comments

[deleted]

Anonymous 0 Comments

What makes it dip is a change in temperature caused by external energy. It’s not moving on its own, although it appears that way at first.

What’s actually happening is there is some clever use of pressure and heat, when the bird dips it’s beak, the felt or whatever on the end gets wet and cools the vapor in the head of the bird into liquid, which more draws liquid up towards the head, making it dip again, then when it’s horizonal the pressure equalizes and the liquid moves yet again to tilt the bird back upright.

Without evaporation of the water on its beak, the liquid/vapor inside won’t change, at least not in the way we want it to.

Anonymous 0 Comments

Ultimately, it’ll stop dipping when the water in the glass evaporates below the level it can reach. The dipping bird extracts thermal energy from the water in the glass to drive its motion.

Anonymous 0 Comments

Thank you for the comments folks, I understand now.

Anonymous 0 Comments

Because it is powered by water evaporating from its head and cooling it, creating a temperature difference, which in turn creates the pressure differences that make the liquid cycle up and down. Once the water source is depleted, the motion stops.

Anonymous 0 Comments

[deleted]

Anonymous 0 Comments

What makes it dip is a change in temperature caused by external energy. It’s not moving on its own, although it appears that way at first.

What’s actually happening is there is some clever use of pressure and heat, when the bird dips it’s beak, the felt or whatever on the end gets wet and cools the vapor in the head of the bird into liquid, which more draws liquid up towards the head, making it dip again, then when it’s horizonal the pressure equalizes and the liquid moves yet again to tilt the bird back upright.

Without evaporation of the water on its beak, the liquid/vapor inside won’t change, at least not in the way we want it to.

Anonymous 0 Comments

Thank you for the comments folks, I understand now.