• Question: how when you mix cornflour with water it makes oblick [non Newtonian liquid]

    Asked by tapo koko to Jake, James, Pete, Senga, Simonne on 9 Nov 2017. This question was also asked by kitty kitty koo koo.
    • Photo: Senga Robertson

      Senga Robertson answered on 9 Nov 2017:

      Hi tapo koko

      I love this question!!

      Ok so you’re totally right, oobleck is a non-newtonian fluid….here’s how it works:

      So if you put your hand slowly in to a mix of cornflour and water and move it around slowly it means that the cornflour particles have time to be displaced (time to move) but if you poke down on the mix quickly the corn flour particles can’t move quickly enough so it feels hard when your finger pokes down and that’s because it’s compressing (squashing) the corn flour particles together.

      Kinetic/ Moon sand is a non-newtonian fluid too….I love moon sand. Did you know you can make your own by mixing cornflour, fairy liquid, water and sand?

      This is the recipe:

      125g of sand, 1/2 a tablespoon of cornflour, 1 teaspoon of fairy liquid and water…(you just add as much water as you think it needs). All you do is mix the sand and cornflour together, and then mix the fairy and water together until it’s all bubbly, pour the bubbly water into the sand mix in little bits at a time giving it a mix each time you do it until it feels like kinetic sand. Easy!

      If you do it and make a big mess and get in trouble you can blame me. lol (seriously though, if you do decide to make it, please check you’re allowed first)

      Senga 🙂

      enjoy the kinetic sand experiment if you decide to do it 🙂

    • Photo: Jake Langham

      Jake Langham answered on 10 Nov 2017:

      Hiya, this is close to my field of research so I thought I’d better add something here! There are lots of different non-Newtonian liquids and not all of them behave the same way as oobleck. For instance ketchup is a non-Newtonian liquid that is kind of the opposite of oobleck. When you hit ketchup it gets more runny (whereas oobleck gets harder when you hit it). This is why if you turn a bottle of ketchup upside-down not much happens at first, but if you hit it a few times… suddenly it all comes out very fast (and goes all over the place usually).

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