COLD HARD SCIENCE.The Physics of Skating on Ice (With SlowMo) – Smarter Every Day 110
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COLD HARD SCIENCE.The Physics of Skating on Ice (With SlowMo) – Smarter Every Day 110

August 11, 2019


Hey it’s me Destin. Welcome back to Smarter Every Day. So in the olympics the most athletic team always wins right? No. It’s actually more complicated than that because there’s physical objects in the olympics. Now the team that is able to manipulate these physical objects better than the other team usually wins. For example, curling. This curling stone is very heavy, and if you can figure out how to manipulate it across the ice better than the other team you will win. So physics is a huge deal and a knowledge of physics is very important. So today on Smarter Every Day we’re gonna start a three part series on equipment used in the olympics and how it interacts with the world around it. Today we’re gonna focus on ice skates. There are three major types of ice skates used in the olympics. The figure skate, the hockey skate and the speed skate. This is my new friend Glenn. He’s a figure skating coach. It’s really awesome. [laugh] So everyone already knows that angular momentum trick right? So large moment of intertia, bringing it in. Small moment of intertia. That’s pretty awesome. So show me your skates. What makes you be able to do that? Cause I mean, I would mess up because of the toe pick, so where are you actually rotating?
(Glenn) I’m actually spinning backwards. My blade is spinning backwards, and I’m spinning on a small area we call the ball of the foot. Also my bottom toe pick is touching the ice. So it’s allowing me to put forward pressure down without sliding forward like I would on a hockey skate.
(Destin) So that’s how you’re able to keep from falling backwards?
– Right.
– Yeah I’m not really getting it. He’s saying he’s rotating about this point but he’s dragging that toe pick. Clearly this is a good excuse to break out the Phantom. Alright. OK now this is making sense. You see I used to think that they pivoted on one spot under the ball of the foot. Looks like I was wrong. They’re actually skating backwards and he’s dragging that toe pick to maintain his balance. That’s pretty cool. Alright, it’s time to move onto jumps. OK Glenn’s gonna show us three of the main jumps in figure skating. Here’s the waltz jump, the salchow, and the flip. There’s a gouge where you left the ice, – I pushed off my toe pick.
– Pushed off the toe pick, and then there’s another gouge..
– And I landed on my toe pick. But then I go down to my blade. So I’m pushing off the ice, and I’m landing on the ice, with my toe hitting first and then my blade.
– OK Glenn’s gonna do a jump and he’s gonna land with his toe pick, which is how they always land. It adds stability. It’s in the landing of these jumps where the design of the figure skates really start to show. You can spike yourself down into the ice with the toe pick and then you slowly rock the blade down. In fact the curvature of the bottom of the blade is called the rocker. After it’s planted firmly on the ground you’ll notice it doesn’t immediately move away. The skater imparts the momentum from his opposite leg back into his lower foot and then he moves. So it’s a three step process. Spike, plant, move. Interesting. But a question I have is that, if the bottom is rounded, how do you sharpen a round blade? So this seems like a good opportunity to move from the figure skate to the hockey skate. So let’s meet my friend Nick who’s the director of hockey operations at UAH. [hockey sticks fall over] So you want to show me.. I’m sorry.
– Second time.
– [laughs] Sorry dude, show me the blade, how’s this work.
– So the blades here, if you look, it’s two separate edges so I’ll draw it up here for you.
– OK. – Blade actually..
– So this is a cross-section.
– Looks like that.
– No way! – A lot of people think it looks like that but it’s actually, there’s a hollow in here.
– Really. – Yep.
– Can we see the sharpener? I like the name [wrestling announcer style] Blademaster! – This is the wheel, which actually sharpens the skate. – How do you hold the blade up there? Is this a sled or something?
– Jig, slider, everybody’s got their own little nickname for it. – OK and so then if the wheel were turning, you would bring that in there let me focus. OK I can see that curvature that you’re talking about, can you go closer if you would to the wheel?
– So that’s the radius of the skate, 3/8ths, half, 5/8ths.
– I’m not sure I understand. You’re saying this hollow right here..
– Yeah some of them will look like that, some of them will look like that, some of them will look like that.
– This is completely eye opening to me. I had no idea that ice skates had two different working edges. So why would a player prefer a deeper hollow vs a shallower one? Well think about it. If you have a shallow hollow you’re able to sit on top of the ice and glide very easily so this is very good for speed. But if you have a deep hollow, your points are gonna cut down into the ice and plow so you’ll go a lot slower however you’ll get much better grip. And if there’s one thing a hockey player needs it’s good grip. Have you ever seen them stop and change directions? So I’ve asked a couple of hockey players to show me how this double edge is used to stop on ice. Behold, the awesomeness of physics! [laugh] Isn’t that crazy? Look at what he’s doing. He’s controlling that edge and scratching the top layer of ice off, but he’s doing it in such a way that it’s converting that shear energy into power which he’s using to decelerate. Some people want to believe that hockey players are just dumb brutes but I’m not buying it. I told this player I wanted him to stop on a very specific spot on the ice. so I could zoom in with the phantom and catch the ice spray, and he did it on the very first try. Can you imagine the math that’s going on in his brain in order to automate this feedback loop? He’s constantly sensing his deceleration and somehow his brain’s converting that information to signals to control the angle of his skates and feather the exact amount of ice that he’s shearing off. To complicate matters, he’s got ice in between him and his target and he has to anticipate the total amount of impulse left in that ice so he can stop exactly where he wants to. Let’s ask him to see if he can explain exactly what he’s doing because I’m pretty sure hockey players are physics geniuses. You don’t gotta take your glove off man Ben, thank you very much. Do you have any, like if you had to say anything about that hockey stop, how exactly do you do it? – Well you’re just trying to find a balance, because you have two, there’s two edges on the skate blade, so you wanna find that inside edge, you know if you get over the top of your outside edge you go over. (Destin) So you’re trying to find that edge on the ice and just shave a fine mist.
– Just the inside one. – So like a noob, somebody that’s just learning how to do that, would they just chatter across the ice? – Yeah. When I started playing I was like three years old so, maybe by the time I was like six I could stop.
– Yeah. – So a couple of years, but like..
– Did you just hit that puck without looking? – Yeah.
– He just hit a puck and you hit it without looking. – I mean I saw it.
– Yep I’m right, they’re geniuses. So if we want grip for a hockey blade we don’t want it for a speed skate right? Which might explain why speed skaters are always falling. This was counterintuitive to me, but the bottom of a speed skate isn’t pointy. It’s actually a flat sharp 90 degree angle. To see speed skaters in action let’s go to the Pettit National Ice Center in Milwaukee and check out the US junior long track championships. OK look at how the skater starts off the line. You see that open stance? They do this because ice skate friction is asymmetrical. They glide easily going forward but they dig in on the sides. So to propel themselves skaters have to push off the sides of the blade. The larger this angle alpha is, the harder they can push. That’s why they line up with their foot at almost a 90 degree angle to the direction of skating. Speed skates are flat which means each individual stride has to be perfectly level when the foot hits the ice. This can be a problem because when you extend your ankle the blade tries to come up off the ice. The solution to this is called a clap skate. Clap skates allow a long track skater to keep their blade on the ice longer into the stride. I’ll let Adam explain. – The clap starts to come out, like this, and once they pick their skate up it just kinda just flies back like that. And so that extra push that makes the clap, gives you a lot more contact on the ice. And so you can get a lot more power.
– All this talk about ice skating and we didn’t even explain why it’s slippery in the first place. So there’s this thing called friction melting. If you’re moving something along ice it creates this really thin layer of water, think like nanometers thick. That is why you can slip on ice so easily. The coefficient of friction can be defined by this equation. It’s very interesting. OK a couple more things you might be interested in. Number one, we’ve been making infographics of all these winter sports. You can go download those and share them with whoever you like. Also I’d like to thank the sponsor that lets me do crazy things like try to explain sports I don’t really understand. So that’s audible.com. You can support Smarter Every Day by going to audible.com/smarter you get a free audio book, whatever you want, they’ve got thousands of titles. I used audible before they asked to be a sponsor for Smarter Every Day so I’m more than happy to suggest that to you. audible.com/smarter Smarter Every Day will get credit, and that’ll help us move forward, do more crazy stuff like this. Speaking of more crazy stuff like this, if you would like to see more videos on winter olympic sports, the next couple of videos, I’m gonna try to get them out pretty quick, are things like curling, and other stuff like that. It’s pretty cool. Anyway, support our sponsor, audible.com/smarter, and if you think we’ve earned your subscription consider that please. I’m Destin, you’re getting Smarter Every Day, thanks for listening to me I appreciate that. Have a good one. Why are you putting your hands out all the time? Why do I always see figure skaters do that?
– Because my coach told me to, over and over. It helps with my balance. Using my arms to rotate, turn myself. And to be a little more dramatic.
(Destin) [laughs] You gotta have a little finesse to it right? That’s awesome. [ Captions by Andrew Jackson ]
captionsbyandrew.wordpress.com Captioning in different languages welcome.
Please contact Destin if you can help.

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  1. One thing you missed is that the small points on the skates create a huge pressure on the ice, which causes it to change state temporarily into water.

  2. Alright…. dude….. honestly I think your over thinking it. Yeah sure your math is probably correct and all but you really think they’re constantly think about exactly how much pressure and blah blah blah to do in the middle of a high paste hockey game? They don’t do the math they just know how to do it. I’m whiling to bet at that level it’s all muscle memory

  3. 5:25 so I’m a hockey player and we aren’t “all” dumb brutes most of us are actually quite intelligent but we don’t really think about the math we just feel it you skate for long enough and it’s just muscle memory

  4. had my skates sharpened at a sports store, almost killed myself, to sharp and no hollow, went to a hockey pro shop, sharpened at 1/2 inch, perfect

  5. As a hockey player, I can stop immediately but I’m not thinking about physics and math… I play hockey to get out of math but I will take the compliment that we are geniuses!!!

  6. i think that he is over complicating it. when you take a fast turn on a bike you automatically lean into the turn so that you don't crash, even tho i have never skated, i have a feeling that it is the same concept.

  7. Pressure melting has been proved to be wrong. Why is it important to point this out? If you google 'pressure melting ice skate' the top site is Scholastic "Teacher's Activity Guide" Which doesn't even get to 'pressure melting,' instead the short explanation says 'ice by itself is no more slippery than a concrete sidewalk!' (wrong) and then explains "the heat generated by the blade of the skate rubbing against the ice causes some of the ice right under the blade to melt.'
    Bad explanations shut down thinking, which leads nowhere. (the NYTimes 2006 has a good article on the subject. I googled because I didn't want to just spout off on you.
    And yes top athletes are geniuses. This is worth a deeper investigation. If you did any sports growing up, you can probably name a dozen young athletes who never made it past high school, or college; they over trained and injured themselves or they just never improved– the kid who was good at everything right at the start, but never learned how to get better. (Shaq came back from basketball camp and told his grandmother, "some of those guys were better than me.'" She asked him, "How many lives do you have?")

  8. @smartereveryday why does fire go up? And why does smoke go towards blown air instead of away from it like it should? What’s the science behind it?

  9. UAH… my school has a weird hockey rivalry with UAH, Bemidji State University in Northern Minnesota had their program founded the same day as UAH's program. We've made it a rivalry thing.

  10. I heard that all three forms of water exist when an ice skate skates. At the blade is ice of course, but that ice is being converted to water and steam. It’s called triple point, and that’s why ice skating is so fast.

  11. Thank you for this. I learned figure skating in the very early 70s. We did not have computers, not even animation for learning how to skate. All we knew was we had 2 edges, we melted the ice under the blade, the toe pick gives us lift and stability, and how to tighten the laces over the arch of the foot, leaving the toes and upper boots looser. I haven't skated in years. But we could "feel" how to stop on the ice without over thinking it. Now, if only I could understand the physics of lift, thrust and spin/centifugal force during a jump. I never understood how that worked.

  12. So if ice is slippery because of nanometer ice melt. you make it to cold for that to happen would you still slide

  13. TO BE FAIR. They are smart of course, until 25 years of bashing in hockey rocks the brain too much. That's what generally makes a lot of athletes become damaged beyond repair.

  14. We all have an intuitive understanding of much of classical physics (how the world works mechanically). We've all used and felt forces, torques, acceleration, momentum. Physics classes gives the theories and formulas.

  15. Hi i am a fan of you.. You and your videos are so amazing… Can you do a video on the science behind the Basketball… Please..

  16. Is there some kind of complex calculus integral that could describe the point at which an ice rink would be too cold for someone to skate on? Like, if you had a hyper-frozen rink would it make it harder to get that nanometer-thick melt layer?

  17. When Destin mentioned the physics going on in the players’ brains, he wasn’t saying that they were consciously doing math equations in their head, rather that their brain can subconsciously calculate the exact angle, velocity, speed, etc of all the maneuvers fast enough to keep up with the game.
    I think his point was that, while they may not consciously understand the math, their brain can calculate everything just fine, showing how powerful the human brain is.

  18. Mm you might wanna look into why is ice slippery a little more 🙂 it hasn't been proven yet last time I looked.

  19. 5:26. I have a pair of skates just like that. it's 700$ full carbon fiber. Very good. bauer vapor apx

  20. Some time in the past someone figured out if you cut a blade in a certain way it allows people to skate well on ice. Did they figure the science out later?

  21. This explains so much!! I tried ice skating once, and a friend showed me how. He just said, angle your blades, but never explained why so I didn't quite get it. And with stopping, I figured out that putting a blade perpendicular to your direction of travel would stop you, but I kept on falling over. That's because I kept my centre of mass was always pretty much directly over where the blade was, so when I was decelerating, my centre of mass slowed down slower than my feet did and caused me to tip. And learning that hockey players decelerate fast by tilting the blade so that one point sheers through the ice plays into that as they tilt their body to add more pressure to the blade, making it difficult a little deeper as well as preventing them from falling over or losing balance at all. This is super interesting, wow!!

  22. I my self ever had hockey practice…. About the "mathematic thing " no not really its honestly just guessing

  23. I didn’t know hockey stop was hard to others but I play hockey and it’s just muscle memory I learned when I was 3

  24. This goes straight into just how unbelievably complex The Lord made our brains. To be able to calculate such things with such accuracy is no mere feat. I see this every time I dabble with physics, especially when working with the Calculus.

  25. What about INLINE speed skating? There's a lot more variables at play. Humidity, wheel compound, wheel dimensions, wheel crowning, amount of flexibility in the frame, track material (wood w/ polyurethane, vinal, concrete, or tarmac), wheel firmness, number of wheels (usually 3 (120-125 mm) or 4 (100-110 mm)), wheel heat, wheel wear, wheel hub streingth, wheel hub material,and the number of mounting points on the frames even. That's what we have to deal with when choosing parts for inline speed skates.

  26. as a hockey goalie, i really love it when figure skaters destroy my crease with their toe picks :))))

  27. The heel mechanism on the speedskates reminds me of an atlatle. I'm sure I'm spelling it wrong but check it out. Extended spearthrowing tool invented by early man. Genius.

  28. "Did you just hit that puck without looking?" 'Yeah' – Like so casually about it, as if to say "Whats wrong with that? Its not hard". Brilliant

  29. @smartereveryday I got to the Petit ice center every once and a while so this is cool to see you were in town!

  30. Destin you should visit my friends in Houston at the urban movement . There's some cool science behind parkour bar balance and laches and different moves

  31. I'm a hockey player and it sucks when figure skaters are on the ice before us because they leave divots in the ice everywhere. ugh just talking about it makes me mad T_T. 2:44 just look at that

  32. I hate to be that guy but ice skates don't work off friction, if they did they would stop working around -40°

  33. I'm going ice skating tomorrow at the centennial sportsplex for the first time and I watched this to hopefully help me, thanks!

  34. I love that sharpness diagram! I use it all of the time and I never knew you guys made it! Also, goalies tend to sharpen their skates to have more bite because we have to be technical in our movements in order to position ourselves to stop the puck. The skaters tend to have less bite because, well, they skate more. It helps them skate faster and they don't need to grip the ice as much as goalies do.

  35. Hockey is pretty easy if you been playing for a year or so you know how to stop quickly and when to start braking PS I play hockey

  36. This is at least my second time watching this video, and I just noticed the awesome editing trick you did with the skate switch but your kid doesn't change. well, either cool editing trick, or AWESOME parenting!

  37. This guy is like imagine all the math they how to consider to stop on that theoretical feedback loop

    Hockey player: I leaned back a little and I stopped moving.

  38. Hey I am a hockey player and when your playing your not thinking about the angle of the skate and all that stuff it’s all muscle memory and just takes practice

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