moment of inertia

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Could cars slow down the Earth?

Time for another Fermi problem. There was a recent story in Science News that talked about the effects of the Chilean quakes on the Earth’s rotation. The basic idea is that some ginmourmous amounts of rock moved closer to the Earth’s center. Since the angular momentum of the Earth is conserved, the angular rotation rate…

Moment of Inertia Demo

When I was talking about balancing a stick, I mentioned the moment of inertia. Moment of inertia is different than mass, but I like to call it the “rotational mass”. What does mass do? Things with larger mass are more difficult to change their motion (translational motion). A similar thing is true for the “rotational…

Maybe you have seen this trick. Basically, you hold by supporting it with two fingers from the bottom. You then move your hand around to keep it balanced while the stick is vertical. It is really not as hard as it looks. Also, there are two things that can make your job easier. Use a…

I saw this video on several places. It shows an astronaut playing with a CD player. I wish I were an astronaut. I would probably not stop throwing up though. It would still be worth it. You can only throw up so much right? (I know the answer to this question). Anyway, this is a…