Wednesday, January 25, 2006

Race you to the bottom!

You have two cylinders with the same dimensions. The weight of both cylinders is identical. One is a massive wooden cylinder, the other one a tube made of iron. When you release them both at the same time on the top of a slope (1 meter at an angle of 45°), which one will be down first?


  1. Probably the one that has the larger circumfrence I would say. Whichever one that would be. Though knowing gravity, they will probably hit at the same time.

  2. The massive wooden cylinder. This has to do with the rotational inertia moment. The iron tube has a very high rotation moment because the mass is situated at a big distance from the rotation axis of the cylinder. The wooden cylinder has the mass more equally divided over the area, the moment will be much less. To accelerate mass you need energy. The lower the moment of inertia, the quicker the cylinder will start moving. Therefore the wooden cylinder will be down first.

    That's why boiled eggs spin faster than raw eggs.

  3. I never noticed nor botherd.

  4. You never spun a boiled egg to compare to a raw one? I thought everyone had done that at some point in their life.


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