How to demonstrate friction using rice

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This particular one involves a bottle of rice and a pencil. Now, in the ah, in a lot of other books and things, they’ll tell you to use a Coke bottle. Now, what we are going to be doing is shoving a pencil into this rice and holding the whole thing up in the air, without it falling off. Now if you do this with a bottle, that’s going to be heavier, and you’re risking it falling off in front of your students, making a complete mess and everyone sort of loses it! So, a better way to go is get a little container here, as long as it’s got like a bit of a bend inwards at the top of the container, you’re OK. Now, I have pre-set this a little bit but what you need to do is, um mean I actually think it’s better from a teaching point of view is actually pour the rice into the container so they can see that you’re not putting into glue or anything… um, it is just rice so I’ve just got it in there for now so I don’t make a mess. What you need to do with the pencil is stab into the rice at different heights. What you’re doing is you’re kind of compressing it. You’re getting more and more air out the container, so you can lift the whole thing up…. … and it’s stuck. Now, it’s a nice easy experiment to do. Ah, if you’re feeling game imagine doing it with groups of students, while they do it at their table! Um, yeah, possible good luck with that 🙂 Might make a total mess! But, the idea is, is that the more points of contact… … between two surfaces… … the more friction. So, what you’re doing is by shoving air out of the way… … more rice granules grab onto the pencil, and eventually, the whole thing just grabs on tight.

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