Olympic Physics: Putting a Spin On It

MJ Author

02/14/2022 Added

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Tim Gay is a physics professor at the University of Nebraska-Lincoln. He’s known for his videos explaining the physics of football. So we asked Dr. Gay to explain the physics behind winter Olympic events. Olympic figure skaters make it look easy. But they use a lot of skill…and a little physics to produce those amazing programs. Dr. Gay explains.

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[00:00:00.670]Have you ever watched a figure skater
[00:00:02.420]put herself into a tight spin?
[00:00:04.930]You may wonder how she's able to move her feet
[00:00:07.150]quickly enough to get herself spinning that fast.
[00:00:10.320]Turns out that the trick isn't in the footwork,
[00:00:12.660]but in the physics.
[00:00:13.810]She's using a principle
[00:00:14.990]called conservation of angular momentum.
[00:00:18.190]Normal momentum, the combination of mass and speed,
[00:00:21.230]corresponds to motion in a straight line.
[00:00:23.960]Angular momentum is important for rotation,
[00:00:27.060]like that of the International Space Station
[00:00:29.580]orbiting the Earth.
[00:00:31.120]Instead of the mass
[00:00:32.470]and the straight line speed of an object,
[00:00:34.770]angular momentum depends on three things,
[00:00:37.620]the object's mass,
[00:00:39.130]it's rotational speed, think revolutions per minute,
[00:00:42.710]and the mass's shape.
[00:00:44.500]For a given mass, the bigger the object is,
[00:00:47.350]the more so-called rotational mass it will have.
[00:00:51.450]The product of rotational mass and rotational speed
[00:00:55.140]is the angular momentum.
[00:00:57.070]Our figure skater goes into her spin with outstretched arms.
[00:01:01.050]Her angular momentum is determined by the length of her arms
[00:01:04.070]and how fast she's rotating.
[00:01:06.170]When she pulls her arms in,
[00:01:08.100]her rotational mass gets smaller.
[00:01:10.720]In order to keep her angular momentum the same,
[00:01:13.850]her rate of rotation has to get bigger,
[00:01:16.200]hence the dramatic increase in her spin rate.
[00:01:19.240]This technique is also used by gymnasts and divers.
[00:01:23.470]So the next time you see one of these amazing athletes
[00:01:26.280]spinning themselves up by changing the position
[00:01:28.720]of their arms or legs,
[00:01:29.990]remember, she's not just going for the gold,
[00:01:33.840]she's practicing the art of applied physics.
[00:01:37.202](gentle music)

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Olympic Physics: Putting a Spin On It

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