How Ice Skaters Turn Physics Into Astonishing Spins
- But if you look at energy (and include mass in the energy), then energy is conserved.Now for angular momentum.
- I think most people are OK with the idea of the angular velocity—but the moment of inertia thing is a bit more complicated.
- Basically, the moment of inertia is a property of an object that depends on the distribution of the mass about the rotation axis.
- If you have more mass further away from the axis of rotation, the moment of inertia is larger than if that was was close to the axis.Here is a super quick demo—and you can try this at home.
- The angular momentum depends on both the angular velocity and the mass distribution of the object.
Conservation of angular momentum is the name of the game.
@WIREDScience: Olympic figure skating provides a great opportunity to talk about the physics of angular momentum
Many people don’t know too much about angular momentum—and that’s fine. But what about figure skaters? Whether they understand the concept of angular momentum doesn’t matter but they use it in one of the all time classic skating moves. You’ve seen it before. The skater starts off in a standing position and spins about the vertical axis. After a few rotations, the skater pulls both arm in closer to the body and spins faster. In physics, we call this conservation of angular momentum.Just as an example, here is this same maneuver performed on a rotating platform instead of on ice.Gif: Rhett AllainReally, you can try something like this on your own. Sit on a nice spinning chair or stool. Start with your arms stretched out as you spin and then bring your arms in. Don’t barf.But what exactly is angular momentum? In short, it is something that we can calculate that can be conserved. That’s a tough definition, so let me give an example of a conserved quantity—like mass (which only mostly conserved). Suppose you take add some baking soda to vinegar. If you’ve ever done this, you will see that the resulting mixture foams and produces some gas. But here’s the cool part. If you measure the mass of the stuff you start with (vinegar and baking soda) it’s the same as the mass of the stuff you end up with (carbon dioxide and water and sodium acetate). Boom, mass is conserved. It’s the same before and after.OK, I…