Question

In one of the physics I lectures, Lewin was able to make a top spin forever (or at least half an hour and more). What's the trick?

Answer 1

The amount of time that the top spins would be a function of its initial angular momentum and the friction of the top against air and the surface its spinning on. Thus, the longest spin would come from a top which is very smooth, has a very smooth tip spinning on a smooth surface (all to reduce friction), and is very heavy, wide, and has a large initial angular velocity. I am of course assuming here that the top is also very well balanced. Basically, its not really a trick, its just a matter of spinning a very good top very fast on a low-friction surface.