Physics

Scientists crack Richard Feynman’s 64-year puzzle about backward-spinning sprinklers

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Mathematicians have resolved the long-standing Feynman sprinkler problem by demonstrating that both normal and reverse sprinklers rotate due to the momentum of flowing water, rather than external water flow or other previously proposed mechanisms. Using experimental "silly sprinklers," the team provided definitive evidence settling a physics puzzle that has perplexed scientists for decades. The research conclusively answers a question famously pondered by physicist Richard Feynman about how sprinklers behave when operating in reverse.


The findings could enable engineers to design more efficient fluid-powered machines by providing a clearer understanding of momentum transfer in rotating fluid systems. This fundamental physics insight may have applications in various engineering contexts involving fluid dynamics and rotational mechanisms.


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A team of mathematicians used whimsical “silly sprinklers” to solve a physics mystery that has puzzled scientists for decades. Their experiments showed that the rotation of both normal and reverse sprinklers is driven by the momentum of flowing water, not by the outside water flow or other long-standing theories. The results finally provide a clear answer to Feynman’s famous sprinkler problem. They could also help engineers design more efficient fluid-powered machines.

Source: “Silly sprinklers” help scientists finally solve Feynman’s famous sprinkler mystery