Aspinning top precesses slowly around a vertical axis through its point ofsupport while it spins rapidly about its own axis. Theeffect is described as precession, and is explained in simple terms below. If it is spinning then it does something else.Instead of falling down, it “falls” sideways. It will indeed fallover if it is not spinning. If the top is perfectlyupright there is no torque acting on it but if it leans sideways then it willtend to fall over due to the torque about the bottom end. Usually, the torque acting on aspinning top is just due to the weight of the top.
Angular momentum is similar to linear momentum,but it refers to motion in a circular rather than a straight line path. In that case, the force on the object is equal to therate of change of its momentum. There is nothing magic about that.It is the rotational equivalent of what happens when an object acceleratesalong a straight line. The torque is equalto the rate of change of angular momentum. The basic physics behind all theseeffects is that a torque is required to rotate an object. It turns itselfcompletely upside down and ends up spinning with its peg underneath the spherethat was originally spinning underneaththe peg used to spin it. Atippe top does something similar, but is even more spectacular. If spun fast enough, a spinning top will rise to a vertical positionand happily stay there, despite the fact that it will fall over if it stopsspinning.Ī spinning egg is just as amazing.If a hard-boiled egg is spun fast enough it will rise up and spin on one end. Aspinning top is remarkable because it tends to defy gravity while it isspinning. Besides, some adults DO play withspinning tops (check the web), and some make very elegant ones (see under spinners). It is also an adult toy, in the sense that it helps to have a PhDin physics to figure out how it works.
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