Friction: Phone Book Friction

This one takes some prep work (you might want to find some student “volunteers” to help you out), but it’s a fun one!

You’ll need two phone books – the larger the better.

You need to shuffle the pages of one with the other. I wish I had a brilliant technique to share with you on how to do this, but I don’t. Do what works best for you. It doesn’t need to be perfect, but the more pages you get interspersed, the more effective.

Now that the books have been joined together as one, have two students attempt to play tug-of-war and pull them apart.

Ha! They can’t do it! Too much friction!

No surface is perfection smooth – they all have bumps of ridges to a various extent. Friction occurs when two surfaces rub against each other and those bumps and ridges catch on each other.

Each of the pages of the phone book has two surfaces filled with ridges and bumps. And, if you’ve done a good job shuffling those pages, there are a whole lot of surfaces trying to slide past one another. Whole lot of pages, whole lot of surfaces, whole lot of ridges and bumps, whole lot of friction!

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Presented by Daryl Taylor at the New Jersey Science Convention.