According to the unearthed stone tools, the spinning top has a history of more than 5,000 years and can be considered the oldest folk toy. A spinning top is a symmetrical object with a thicker end at one end and a thinner end at the other end. If the pointed end of the spinning top is placed on the ground, due to the center of gravity being above the fulcrum, it will immediately fall over when the hand is released. If the spinning top is swung out with a thin rope and then spun on the ground with a whip, it can stand upright without falling over. It can be seen that the magical vitality of the spinning top comes from its rotational motion.
According to the principle of inertia, if there is no external interference, the axis of rotation of an object rotating around an axis will maintain its direction in space. This conclusion can be confirmed on the Earth where we live. The Earth rotates continuously around an axis passing through the North and South Poles, and the axis of rotation always points towards the North Star. If the spinning top is not disturbed during rotation, the axis of rotation can also maintain a vertical position permanently. However, interference is always unavoidable. When the spinning top is disturbed, if the axis of rotation deviates from the vertical axis, the force of gravity on the tip supported by the ground will no longer be in the same line. If the object is not rotating, the torque of gravity on the support point will cause the object to tilt towards the direction of the torque. But it cannot make the rotating object tilt over. Due to the inertia of rotational motion, the torque can only make the axis of rotation deviate towards the horizontal direction. Under the continuous action of torque, the axis of rotation will draw a conical surface in space around the vertical axis, which is called the precession of the spinning top. When the spinning top rotates at a high speed, the angle of deviation of the axis of rotation is very small, and the conical motion almost coincides with the rotation around the vertical axis. If the spinning top stops spinning, the precession phenomenon can be clearly observed. The smaller the speed of rotation, the greater the angle of deviation caused by interference. When the speed of rotation is very slow, the spinning top will completely fall over.
The spinning top is another traditional spinning top game. The spinning top is divided into single-wheeled and double-wheeled. The double-wheeled spinning top has a disc installed symmetrically at both ends, and the two directions of the gravity torque are opposite and cancel each other out, so the axis of rotation of the spinning top can maintain its direction unchanged. The person spinning the double-wheeled spinning top can stand still on the spot. The single-wheeled spinning top only has a disc installed at one end, and the gravity torque of the disc causes the spinning top to precess. The person spinning the single-wheeled spinning top must spin with the spinning top on the spot so that the spinning top will not fall off the string.
The phenomenon of using the inertia of rotational motion to maintain the direction unchanged of the axis of rotation is also applied in real life. For example, making the fired bullet or shell rotate can avoid the bullet from tumbling in flight, thus improving the accuracy of shooting. Similarly, the artificial Earth satellite rotating around a symmetrical axis in space can maintain a stable attitude. China's first artificial Earth satellite, "Dongfanghong No. 1", is an example of a spinning satellite stabilized by rotation.