Why doesn t the gyro fall when it spins, what does the spinning top not fall down

If it falls, the angular momentum is not conserved, and the angular momentum is a vector quantity, with direction.

However, the gyroscope will still fall in the end, and there will be a loss of energy due to the presence of friction when turning.

I don't think there's something wrong with the melodious statement. As Lz himself asked, the circular motion of the center of mass should be within the horizontal plane, whereas the vertical gravity cannot have a horizontal component to provide the centripetal force. I think that if you only consider the center of mass, the centripetal force should be provided by the resultant force here, because there is also support and friction at the fulcrum.

When considering the rotation of the gyroscope, of course, it cannot be regarded as a particle. The rotation axis that Melodious refers to rotates around another axis of rotation is a phenomenon called precession. Generally we don't interpret it in terms of centripetal force, but by using torque.

Since the axis of rotation is not perfectly upright, gravity has a moment towards the fulcrum. If the top starts at rest, the effect of this moment is to tip the top down. When the gyroscope rotates at high speed, the gyroscope itself has an angular momentum, and the result of this moment is to change the direction of the angular momentum, that is, the axis of rotation of the gyroscope turns at a certain angle.

To put it simply, during the rotation, gravity does something else (precession the top), so the top doesn't fall. It's similar to when a satellite is in orbit, gravity causes it to spin instead of falling.

It's hard to explain without a picture... Since LZ is so interested, you can find some physics books in universities to read, which are generally covered in the chapter on rotation.

Gyroscope characteristics - axis fixation The top does not fall down during rotation, thanks to the first characteristic of the gyroscope, which is called axis. When the gyroscope is rotating, if the moment of the external force acting on it is zero, it can be seen from the angular momentum theorem that the angular momentum of the gyroscope for the fulcrum is conserved, and the direction of the angular momentum remains unchanged in motion. Each point on the top rotates in a circle in a plane perpendicular to the axis of rotation.

According to the law of inertia, every point tries to move itself away from the circumference at any time along a tangent of the circumference, but all the tangents are in the same plane as the circumference itself. Therefore, each point tries to keep itself in the plane perpendicular to the axis of rotation when it is in motion. The conservation of angular momentum is seen everywhere in life.

When a figure skater folds her hands or hugs her chest, the distance from the faux part of her body to the reels decreases, the angular velocity of rotation increases, and the athlete spun rapidly.

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Gyro Characteristics – Precession The second characteristic of a gyroscope is precession. When the gyroscope rotates at high speed, the central axis of the gyroscope seems to be rotating around an erected pole, and the phenomenon that the axis of the object rotates in space at high speed is called precession. This is because when the gyroscope is subjected to the moment of gravity on the fulcrum, according to the angular momentum theorem, the vector direction of the angular momentum follows the rotation of the gyroscope, tracing a cone.

In fact, due to the tidal forces exerted by the sun and the moon, our earth has been constantly and slowly precession, and the long-term precession is called precession. In our daily life, we can often see precession, for example, when the bicycle is moving, if it is slightly skewed, as long as the front of the bike is slightly turned in the other direction, the car will be balanced. It is gravity that creates a braking torque on the tire fulcrum, which causes the car to return to balance.

When the gyroscope rotates, the axis of rotation is generally not vertical, when the axis of rotation is deviated, the lower end of the gyroscope (generally a grain of iron ball) is not located in the axis of rotation in contact with the ground, which will produce the friction force that translates the center of mass, so that the axis of rotation rotates around another axis of rotation, that is, the spinning top that we generally see is not fast and still circles on the ground when it rotates, just like the earth rotates around the sun when it rotates itself, so that the center of mass is moving around another center, so that centripetal force is needed, The component of gravity towards the center (due to the tilt of the axis of rotation) provides exactly this centripetal force, making it dynamically balanced. Therefore, it will not fall, and when the velocity decreases, it is not enough to produce a translational velocity with a large enough centroid of mass, and the centripetal force required is less than the centripetal force of gravity pointing to the center, and the gyro immediately falls. Therefore, it is impossible for the general spinning top to rotate vertically, it must be tilted and move around another center, but sometimes it is too subtle to be seen.

Just like a bicycle, no one can ride a bicycle along a straight line, they are all doing curvilinear movements with large or small radii, borrowing centripetal force from the gravitational component to achieve the purpose of dynamic equilibrium.

Why does the gyroscope rotate without falling? Put it on the cotton line and observe, I can't believe it after reading the process!