0:00:05 > 0:00:08This is Blue Peter, but mini.
0:00:08 > 0:00:13Expect epic adventures, mates, bakes, badges, pets,
0:00:13 > 0:00:15presenters and your post.
0:00:15 > 0:00:18We've only got five minutes, so get ready for your Blue Peter adventure.
0:00:22 > 0:00:24We're in a top secret facility
0:00:24 > 0:00:27because I'm taking on a very special challenge.
0:00:27 > 0:00:31We're putting the laws of physics to the test.
0:00:31 > 0:00:34We're going to be taking on one of its most famous forces to
0:00:34 > 0:00:37push science to the limit.
0:00:37 > 0:00:40This is Mission Friction.
0:00:40 > 0:00:43This year the BBC launched Terrific Scientific, which is
0:00:43 > 0:00:46all about getting us excited by science.
0:00:46 > 0:00:50We wanted to get involved in the biggest way possible, so I've called
0:00:50 > 0:00:55upon science expert Greg Foot to help us test the powers of friction.
0:00:57 > 0:00:59Greg, I'm so glad you're here to help out.
0:00:59 > 0:01:01Firstly, please tell me - what exactly is friction?
0:01:01 > 0:01:04Right, so whenever you take two objects and they touch
0:01:04 > 0:01:08- or they rub together, you get a force of friction between them.- OK.
0:01:08 > 0:01:11- Try this. Rub your hands together. - Yeah.- What do you feel?
0:01:11 > 0:01:12They're getting hot.
0:01:12 > 0:01:13Yeah, exactly,
0:01:13 > 0:01:16so you're having to put in energy to overcome that friction, and some of
0:01:16 > 0:01:20that energy is getting transferred into heat, which you can feel.
0:01:20 > 0:01:23OK, so how do we actually test friction?
0:01:23 > 0:01:26I thought you'd never ask.
0:01:26 > 0:01:28- What exactly is this? - I've wanted to do this for ages!
0:01:28 > 0:01:32This is the recreation of a very famous experiment that takes
0:01:32 > 0:01:33two books...
0:01:33 > 0:01:36And then it interleaves the pages together.
0:01:36 > 0:01:37You take the bottom page from this book
0:01:37 > 0:01:40- and then you put the bottom page from this book on top of it.- Oh!
0:01:40 > 0:01:41And then a page from this and a page from this,
0:01:41 > 0:01:44kind of wrapping the pages on top of each other, interleaving them
0:01:44 > 0:01:47and you're left with that. And then they lock together like that.
0:01:47 > 0:01:50- I can't imagine how many hours that takes.- SO long!
0:01:50 > 0:01:54For this test, we're using two chunky books, and the rubber band
0:01:54 > 0:01:58is there purely to keep the book covers from flopping about.
0:01:58 > 0:02:00It's going to take a massive force to pull it apart.
0:02:00 > 0:02:02- Yeah, but the question is, how massive?- Ha-ha!
0:02:02 > 0:02:06Well, we need something quite a lot stronger than us, that's for sure.
0:02:06 > 0:02:10How about two vans which will drive in opposite directions to try
0:02:10 > 0:02:12and pull the books apart?
0:02:12 > 0:02:14And what I've done is I've put in this thing,
0:02:14 > 0:02:16this is called a load cell.
0:02:16 > 0:02:19What this is going to do is tell us the maximum amount of force that
0:02:19 > 0:02:23these vans are pulling on either side of this bad boy book rig.
0:02:23 > 0:02:25What's going to happen, is it going to rip,
0:02:25 > 0:02:28is it going to survive? There's only one way to find out.
0:02:28 > 0:02:32Three, two, one... Pull!
0:02:35 > 0:02:36Look at that!
0:02:36 > 0:02:37TYRES SQUEAL
0:02:37 > 0:02:39Try harder!
0:02:39 > 0:02:40That's unbelievable.
0:02:42 > 0:02:43She is smokin'!
0:02:43 > 0:02:45- Woohoo!- Let's see what happened.
0:02:45 > 0:02:47- Let's go in, are we good?- Is it safe? Yeah.
0:02:47 > 0:02:48We're coming in, guys!
0:02:48 > 0:02:53- I can't believe this didn't break. - 1,167kg.- So what does that mean?
0:02:53 > 0:03:00That is like hanging 18 adults off this book rig. But you know what?
0:03:00 > 0:03:03- I think we can take this bigger. - What do you mean?
0:03:03 > 0:03:05To be honest, you really do not want to know.
0:03:10 > 0:03:14Greg has a super-sized experiment that will really test these
0:03:14 > 0:03:18books, and it's all going to take place at the home of Blue Peter,
0:03:18 > 0:03:21at Media City in Salford.
0:03:21 > 0:03:27- So, Greg, we've built our own mini Media City here.- Yep.- Why?
0:03:27 > 0:03:34My plan is I want to dangle you underneath those interweaved books.
0:03:34 > 0:03:40Attach the other end to a zip wire, OK, so this is you here,
0:03:40 > 0:03:45and then send you 235 metres down a zip wire,
0:03:45 > 0:03:52all the way down into the piazza, dangling using nothing but friction.
0:03:52 > 0:03:54- Is this a joke, are you joking?- No.
0:03:55 > 0:03:58I actually can't get my head around that.
0:03:58 > 0:04:01This is a proper, proper Blue Peter challenge,
0:04:01 > 0:04:03it doesn't get more extreme than this.
0:04:03 > 0:04:07This challenge is so big, we need another presenter,
0:04:07 > 0:04:12someone with nerves of steel, and a matching suit, we need Radzi.
0:04:15 > 0:04:20As we get into position, 35 metres up, it all becomes sickeningly real.
0:04:20 > 0:04:22I didn't think it was that high.
0:04:22 > 0:04:25And now that we're up here, looking down to where I need to go,
0:04:25 > 0:04:27- oh, my tummy just went.- That's a long way.
0:04:27 > 0:04:30My tummy just went. I feel a bit sick. I'm not going to look...
0:04:30 > 0:04:32I'm just going to look... I'm going to look this way.
0:04:32 > 0:04:34- Do you want to step over here, then?- No, I don't.
0:04:34 > 0:04:37Come on, it's not as bad as you're making out, you know that.
0:04:42 > 0:04:45- You ready to go? You look ready to me.- No. Oh!
0:04:45 > 0:04:48No, no, No, I feel really scared! Do I... What do...
0:04:48 > 0:04:51I'll keep my arm here a minute, so you come and shuffle up to my arm.
0:04:51 > 0:04:53Why are we trusting a book to get me to the other... Ugh!
0:04:53 > 0:04:56I've just looked over again...
0:04:56 > 0:04:57Here we go, here we go, here we go!
0:04:57 > 0:05:01- Five...- Four...- Three...- Two...- One!
0:05:01 > 0:05:03Go!
0:05:04 > 0:05:06SHE SCREAMS
0:05:07 > 0:05:10It's just the friction between those pages!
0:05:11 > 0:05:13I'm going so fast!
0:05:17 > 0:05:21- I cannot believe that worked! - How was it, Linds?- I'm crying!
0:05:22 > 0:05:24Get me off, get me off!
0:05:24 > 0:05:26- It worked!- Mate, that was amazing.
0:05:26 > 0:05:29You know what, the speed really picked up.
0:05:29 > 0:05:33About halfway through, that went from being fine to actually,
0:05:33 > 0:05:34how am I going to stop?
0:05:35 > 0:05:39The whole way I was like, "Come on, science! Come on, friction!"
0:05:39 > 0:05:41I wasn't nervous at all watching Lindsey.
0:05:41 > 0:05:45But now I know that I'm using the same books that she used
0:05:45 > 0:05:48and the weather's getting worse and it's raining...
0:05:48 > 0:05:51Well, think about what normally happens when paper gets wet.
0:05:51 > 0:05:54- It gets all soggy and mushy.- Yeah, and it tears easily!
0:05:54 > 0:05:57Yep. I don't think it's going to be able to take as much load on it
0:05:57 > 0:05:59- as soon as it gets wet. - Oh, don't say that, Greg.
0:05:59 > 0:06:01Come on, come on, Radz... I think he's near.
0:06:01 > 0:06:04I'm going to do it! Wish me luck.
0:06:05 > 0:06:10So will two soggy books hold Radzi's weight for 235 metres
0:06:10 > 0:06:12at speeds of over 25mph?
0:06:12 > 0:06:14Cue the countdown.
0:06:14 > 0:06:20- Five...- Four...- Three...- Two...- One!
0:06:20 > 0:06:23Woohoo!
0:06:31 > 0:06:35The harness seems to work!
0:06:41 > 0:06:45- Hey!- Greg, you're right! It works!- Science works!
0:06:48 > 0:06:51Join in every Thursday on CBBC!