Wed February 12, 2014
Scientist Talks The Formulae For Olympic Success
Originally published on Wed February 12, 2014 8:00 pm
MELISSA BLOCK, HOST:
Olympic sports are marvels of power and beauty. They're also marvels of physics. Take ski jumping. Skiers launch themselves into flight at speeds up to 60 miles per hour. They fly through the air for the length of a football field or more and land usually gracefully. We asked physics professor John Eric Goff, at Lynchburg College, to explain the physical forces at work in ski jumping. He wrote the book "Gold Medal Physics: The Science of Sports."
JOHN ERIC GOFF: Well, they've started from the top of the hill. They've gotten to the launch point. The arms are backward. They are bent at the waist. They're trying to reduce the amount of air that's hitting their bodies and that's key because the launch speed is what they're trying to increase and once they leave the ground, they're finished. They can't do anything else on that hill to help them with their launch speed.
And once they're up in the air, then they hit the same V-style with the skis and they're like a glider in flight.
BLOCK: Yeah, and I was interested to read that that V-formation where the skis are out in a V and they're leaning way forward over the skis with their arms back that that's a pretty new invention for ski jumping. It's only been the last 20 or so years that they've been doing it that way.
GOFF: In the old days, you would see skis straight. And what science has shown is that you get about 30 percent more lift in that V position compared to the skis being straight out. In fact, the birds have figured this out through evolution that they could separate their feathers a little bit and help generate a little bit more lift.
Once the skier has left the snowy earth behind, what happens is the skiers going to be fighting air drag. They need to be incredibly flexible. They will lean down, you know, 10 degrees or so off their skis and the skis are opened, you know, might be 30 degree angle, 40 degree angle. That enhances the lift.
BLOCK: What about the impact of landing?
GOFF: So the hill is going to be sloped and it's a good thing. When the skiers are coming down, it's nice to land on the hill that's sloping away from you because if the hill was completely flat, there would be a large component of the force backwards so not only are you being stopped vertically, but you're begin stopped horizontally as well.
So the gradual reduction in the slope allows them to land and ski forward and come to rest a little more gradually.
BLOCK: But things can go terribly wrong. I was reading about an injury that Lindsey Vonn, the ski jumper, suffered where the force of the landing - it's a horrible description - jammed her leg bones together and her knee cartilage essentially exploded.
GOFF: That's right. And, of course, the knee cartilage is there to take away some energy. It's like a sponge or a spring if you want to think of it that way. So when we walk, we don't hurt because we're transferring a little bit of that energy into our cartilage. If you land very hard like she did, the force here gets several Gs so several times your weight and what happens is that compression just goes well beyond what it's capable of keeping the bones apart.
And yeah, you could do some serious damage on a bad landing.
BLOCK: I was thinking as you watch the Olympics as a physics professor, you must be watching it in a very different way. I mean, you're looking for all these laws of physics that are applied there.
GOFF: And one of the criticisms about science in sports is that sometimes it's, you know, reducing these great athletes performing at the pinnacle of their metier down into equations and it's absolutely not what's happening. I mean, a deep understanding of, you know, the laws of physics and how they apply to all of us and especially the athletes that we see in the Winter Olympics, it adds as sense of beauty.
What those athletes can do with enormous training, mental focus, the, you know, core strength, flexibility, they're really at the limits of what physics says can be done.
BLOCK: Well, professor Goff, it's been great to talk to you. Thanks so much.
GOFF: Sure, Melissa. I enjoyed it.
BLOCK: That's John Eric Goff. He's author of the book "Gold Medal Physics: The Science of Sports," and he chairs the physics department at Lynchburg College in Virginia. Transcript provided by NPR, Copyright NPR.