Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

## Tuesday, 10 January 2012

### Rock, Paper..Water?

As I was playing rock, paper, scissors the other day, I thought how stupid it was that paper beats rock. I mean, sure, it covers it…but that’s about all. So I was wondering if I could come up with a better trio to play the game with. And because all thoughts in my brain lead to science I thought I should share some of the match-ups I considered

Rock v Water

Seems simple, right? Rock goes in the water, and you could argue that the rock wins as it stabbed through the water, or that the water wins since it absorbed the rock. I’m thinking more technical though. When water freezes it makes ice, which we know takes up more volume than as a liquid (test this by filling a water bottle full and putting in the freezer, it’ll be all swollen). In cold places, water creeps down the holes in rocks, then when it freezes, pushes the rock apart, over time splitting huge bits of rock off. So, water most definitely beats rock then.

Paper v Chalk

Chalk writes on paper, paper gets written on, seems fairly straightforward that chalk wins. But don’t be so hasty! Have you seen those card throwers? Go on – look them up on youtube, I’ll wait. They have the ability to cut, pierce and slice with nothing but a playing card or business card and the right throwing technique. It’s all about the pressure that you can create with the card edge, and pressure comes from force. A flying card has plenty of forwards thrust thanks to the thrower, and combine that with the tiny area of the card edge and you can see how easy it would be to get the card to pierce something…like a piece of chalk. So, paper could win!

Water v Paper

If this was a game played with hands I wouldn’t like to try and guess how water would be done, but thankfully that’s not part of the problem I’m worrying about here! Paper goes in the water and gets soggy seems like too much of an obvious answer here. Let’s imagine we’ve got a piece of paper that won’t get soaked too easily, like a playing card again. Take a glass of water, put the card over the top and carefully turn upside-down. Now lift up the glass… Careful! You’ll find that the paper has trapped the water, thanks to the way that the water forms a seal and won’t let more air in, effectively creating a semi-vacuum that holds the water up.

So it seems that rather than creating a new game that actually works, I’ve just been busy defending poor paper. Not just “wins by covering rock” but much more awesome than that, thanks to a few little bits of physics. Paper cuts rock (well, chalk) and paper traps water. Go paper! I’ll always choose you now. Just beware the scissors, there’s nothing that can save you there.