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I just saw a YouTube video about Non-Newtonian fluids where people could actually walk on the surface of the fluid but if they stood still, they'd sink. Cool stuff.

Now, I'm wondering: Could a pool of Non-Newtonian fluid stop a bullet? Why or why not?

If so, if you put this stuff inside of a vest, it would make an effective bullet-proof vest, wouldn't it?

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It doesn't have to be non-Newtonian. Water stops bullets if you have enough of it. Armour does not stop bullets if you don't have enough. – james large Oct 5 '15 at 18:21

Yes, here is an example where they made a bullet proof vest by soaking Kevlar fabric in a non-newtonian fluid:

The video is from 2006, I don't know if this has been developed further.

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This would be a great answer if you write about the contents of the video. – David Z Jul 11 '12 at 22:05

BAE Systems have already done this. Annoyingly there seems to be some problem on the BAE web server at the moment, but there's a description here with links to the BAE site. Alternatively Google for something like "liquid armour".

Dilatant fluids are very good at absorbing energy as forcibly shearing them requires evaporating the water between the particles, and this absorbs a lot of energy. There is more info about dilatant fluids in the answers to Why do non-Newtonian fluids go hard when having a sudden force exerted on them?

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Actually non-neutonian fluids are a bit heavy and massive with regard to their bullet stopping efficiency. They could work with other approaches.

This does not mean their tension surface is infinite. They are penetrable and a bullet applies huge surface tension

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