Name: 寒冷的硬科學.冰上滑冰的物理學(與SlowMo)--每天更聰明 110 (COLD HARD SCIENCE.The Physics of Skating on Ice (With SlowMo) - Smarter Every Day 110)
Uploaded: 2021-01-14T06:23:13.000Z
Duration: 9 min 48 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Hey it's me Destin. Welcome back to Smarter Every Day. So in the olympics the most athletic team

轉承詞

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.

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,

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.

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