Header by Rory Midhani
Happy Hunger Games Olympics! Have you braced yourself for the next lurching round of naive/misguided vs. brave/wonderful athlete comments on LGBT people and Russia? It’s going to be gruesome, I can already tell. So today we pause, momentarily, for a half-step sideways into the intersection of two other awesome international spectacles intermittently fraught with weird political controversy: science and the gayest Olympic sport since the International Olympic Committee dropped wrestling.
Yes, today we’re talking about the physics of figure skating.
Helping us out today will be my favorite lady skater of 2014, Yuna Kim. Going into the Sochi Games she will be defending her 2010 Olympic gold. Among numerous other titles, Kim is the reigning two-time World Champion, a three-time Grand Prix Final champion and a six-time South Korean national champion.
Coincidentally, she’s a total heartthrob dreamboat cutie pie:
So lace up, and let’s talk some science!
FYI, it’s also okay if you just want to look at these gifs and follow the links for videos of Yuna Kim. Did you know she’s also a singer?! Gif via Daum Blog.
Let’s start at the very beginning: ice. Frozen water. A material that’s perfect for skating on because it has such little friction — scientifically, the force that occurs when two objects slide against each other and dissipate their energy of motion.
Ice skates are designed to take advantage of this with their grooved blades that are only one-eighth of an inch thick. Because of the minimal contact with an already low friction surface, skaters find little resistance as they slide against the ice and can glide smoothly.
Yuna experiments with friction. This was from the 2009 Festa On Ice, where Yuna performed in a group routine to “Dancing Queen” and “It’s Raining Men” with Johnny Weir.
Skilled figure skaters propel themselves across the ice in controlled motions by taking advantage of Newton’s third law of motion: for every action, there is an equal and opposite reaction.
For example:
Michelle Kwan and Yuna Kim hold hands going into a T-stop at the 2010 All That Skate LA.
At the start of the movement when Yuna angles her right foot outwards and extends her knee behind her, the broad edge of her blade hits the ice creating friction. When she pushes to make the edge exert a force, the friction propels her forward. In other words, when Yuna pushes against the ice, the ice pushes back. This is how she and Michelle are able to perform their T-stops at the end — by using friction to push in the opposite direction of their motion.
The same action-reaction principle also comes into play during jumps: when a skater forcefully pushes down, the ice forcefully pushes up, launching the skater into the air to perform whatever feat their heart desires.
Closeup of Yuna’s skates during a triple lutz – triple toe loop combination. I like when the jumps are slightly imperfect because it reminds you how absurdly difficult they are. Gif via Kodemari Sakuraweb.
When figure skaters jump, their entire bodies become projectiles (objects upon which the only significant outside force acting is gravity) moving both vertically (up in the air and back down again) and horizontally (across the ice). The key concept here is Newton’s third law, inertia: a body in motion tends to stay in motion. Because the only force in play mid-jump is gravity, the motion path is that of a parabola (an inverted, stretched out “u” arc).
Ignore the spinning for a minute and check out the path Yuna’s body follows:
Yuna executes a flawless double axel at the 2009 Grand Prix Final Gala. Love those sparkle pants. Gif via Naver Blog.
Moving across the ice, Yuna’s horizontal velocity (speed in a particular direction) stays more or less constant throughout the move. Compare this to her vertical motion (Yuna goes up a certain height, stops, and reverses as gravity pulls her back down) and you can see that the forces are independent of each other (meaning that changes in one are not necessarily mirrored in the other).
Here’s another jump with some freeze frames:
Combination triple lutz triple toe loop at 46th Golden Spin of Zagreb. Gif via YunaKimFan.com.
Now let’s take a look at the rotation — which, scientifically, is measured via angular momentum (the amount that a body is rotating about a point).
Observe Yuna’s arms throughout the jump:
Triple salchow at Summer 2012 All That Skate.
Just as she did in the previous jumps, Yuna starts her salchow with her arms reaching out like she’s getting ready for a giant bear hug. As the jump begins, Yuna swings her outside arm around in front of her body. As she goes up, she pulls both arms in close to her body and does a few quick turns in the air; then at the end of the jump, she extends them out to either side again.
Aside from looking elegant, these arm movements actually serve the purpose of speeding up and slowing down Yuna’s rotation via the principle of conservation of angular momentum.
The idea here is that that when rotational inertia decreases, rotation speed increases; or when the rotational speed decreases, the rotational inertia increases. There are no outside forces causing Yuna’s body to rotate after she initiates her spin, so practically, pulling in her arms in reduces her rotational inertia and causes her to spin faster.
You can see the same principle in action with her free leg, particularly in jumps assisted by the toe pick, such as the flip and the lutz. Pulling it in helps her to rotate faster.
Boom. Triple flip at the 46th Golden Spin of Zagreb. Gif via Kodemari Sakuraweb.
Similarly for spins performed on the ice, Yuna’s speed increases as she pulls her limbs inwards, making her body more compact. She slows herself down by doing the opposite, unfurling her limbs.
Watch her change her speed:
Zagreb again. This full routine, set to “Send in the Clowns,” is what she’s expected to perform at the Olympics. Gif via Wikitree.
And here’s Yuna doing another spin, because why not:
Yuna in a layback spin at the 2009 Ice All Stars group closing number. No speed changes to be seen here, but isn’t it beautiful? Gif via Happy Skater YunA Kim.
Enjoy the Olympics, everyone!
Notes From A Queer Engineer is a recurring column with an expected periodicity of one month. The subject matter may not be explicitly queer, but the industrial engineer writing it sure is. This is a peek at the notes she’s been doodling in the margins.
This is very good. I think figure skating physics should go on a list of sexy science along with dinosaur facts.
Finally an article on here that is super interesting to me. Love engineering (so far. Ask me again when im a senior). I wish you guys had more articles by scientists. (And not just biologists/scientists that deal with cats).
S.A.C., it’s nice to hear we have kindred interests! Just in case you haven’t come across these yet, can I point you in the direction of Vivian’s Queered Science column? And perhaps the science tag and Ali’s Queer Your Tech column? They make my engineer heart beat fast, and I suspect you’ll find more of what you’re craving there too. :)
YES YES YES YES YES. thank you so much!
Also may I suggest covering the first conference of “scientista” at MIT on April 5th? Its all women in STEM. It’s gonna be great. Although I’m biased because I may be presenting research.
This is just the dang coolest thing on the internet today.
I agree!
this is neat as hell. it’s cool how humans are just a collection of simple machines, like everything else, and we’ve found so many ways to work with that and do beautiful things.
I did not know this beautiful human existed until today! I do not regret watching that Yuna Kim “Seductive ice show ‘Fever'” video.
Also, this post is super rad.
I’ll never see figure skating in the same way again c:
Science!
Neato post… which immediately reminded me of the movie Ice Princess haha.
It’s science!!!! Don’t you just love the magic of science? It never fails to interest you.
A refresher of physics 1 in an entertaining manner. Love it.
Awesome article with lots of lovely science for my brain. But most of all, happy to see Yuna Kim here on autostraddle! Thank you~
WOOOO as a pure math person, i rarely see applied stuff. and in my grad analysis on manifolds course the other day we briefly talked about velocity vectors on curves and whatnot. Love this.
Also she’s an amazing figure skater!
I needed to share this advert from the tv channel showing the paralympics in the UK and wasn’t sure where was best to out it…so I’m going to leave it here.
http://m.youtube.com/watch?v=-6RID82Ru-k&desktop_uri=%2Fwatch%3Fv%3D-6RID82Ru-k
Unhand that svience!
Or science, whatever.
This makes me feel incredibly unproductive today
If only my physics prof had used gifs of Yuna to illustrate lectures…I might have actually cared about angular momentum.
Seems to me that an enginner would know to count revolutions :-) Yuna does a double axel in that gif. She’s never landed a triple axel (the only ratified landings by women have been by Tonya Harding, Midori Ito and Mao Asada). But other than that, a great read!
Ooh, you’re right. Fixed! Thank you!
OMG that video why hasn’t anyone ever told me about the existence of it?!? Physics, you say? Very interesting. Can you move a bit to the left yeah sdfgljksldkfjglksjdfg *ded*
PS: I did read the article and I did find it very interesting. BUT THAT PERFORMANCE JESUS I can’t stop replaying it! Why didn’t anyone alert me about the existence of such a thing What good are you, Autostraddlers, huh? HUH?
good to see a fellow queer physics nerd on auto straddle :)
love this!
The handwritten formulas were the best part. :3 Maybe I would’ve done better in physics back in high school if there’d been figure skating babes involved..
This is a really fantastic analysis. I loved the jump with the freeze frames. Hard to believe that people can make all these minute adjustments so quickly.
Waah super cool!!! Oh, physics…
Super stoked for the science lesson but even more stoked that I now know how to spell salchow
Anyone else flashing back to that Disney movie starring the chick who played Dawn, in which she’s a physics prodigy who uses her knowledge to become a brilliant ice skater? …Just me? OK.
I love Yuna Kim. And this article really helped to explain the physics of figure skating. I have been wondering about how this all connects together because I have been figure skating for 4 years. Thanks autostraddle!??
Isn’t inertia Newton’s first law of motion?