So, in a cheating nutshell, tops stay upright because falling over violates angular momentum. Of course, it will eventually fall over due to torque and friction. The torque from gravity creates a greater and greater component of angular momentum pointing horizontally, and the friction slows the top and decreases the vertical component of its angular momentum. Once the angular momentum vector which points along the axis of rotation is horizontal enough the sides of the top will physically touch the ground. Essentially, tops prefer to spin on a very particular axis, which makes the whole situation much easier to think about.
However, for centuries creative top makes have been making tops with very strange moments of inertia that causes the tops to flip or drift between preferred axises, which makes for a pretty happening 18th century party. Both momentum and angular momentum are vector quantities, that is they both have magnitude and direction. You said only angular momentum was a vector. If you have a top with a motor turning it at constant speed mounted on a cylinder, it will force itself upright…correct?
Now in the same scenario, you have a servo mounted on the cylinder and its shaft is parallel to the cylinder. Its purpose is to rotate the mount of the top. If the servo turns the mount for the top 45 degrees in either direction, the top will try to keep its upright position? Does this mean that the entire assembly will now be at that 45 degree angle without falling over? If so, will the top force the entire assembly to move in any direction parallel with the ground? A top shall begin to wobble as it loses mechanical, or kinetic.. If a top is perfectly balanced.. A spinning top remains upright for the duration of the spin because the speed causes atmospheric conditions..
By the time gravity gets the chance to act on a particular spot on the top.. Notify me of follow-up comments by email. Notify me of new posts by email. It's a collection of over fifty of my favorite articles, revised and updated. You should buy it. Click the photo for a link to the amazon page, or this link for the ebook. Do time and distance exist in a completely empty universe? Do you need faith to believe in science?
Now suppose that gravity causes the top to fall to the right, as viewed from the front. Both momentum and angular momentum are vector quantities, that is they both have magnitude and direction. See Eur J Phys Dec Lovitz offered an alternate explanation: The same thing would happen if you tried to balance a pencil on one end on the table and tilted it sideways slightly so that it falls. Gyroscopes, tops, and everything that spins are seriously contrarian dudes. Liquid flows back to the bottom bulb, and its shifting weight restores the bird to its vertical position.
What keeps spinning tops upright? Posted on January 22, by The Physicist. So, without getting into that: The right hand rule. Email Print Facebook Reddit Twitter. A simple explanation of precession can be given in terms of the diagrams below. Suppose that a top is spinning counter-clockwise viewed from above and suppose it is upright, as drawn on the left side of the diagram. Now suppose that gravity causes the top to fall to the right, as viewed from the front. Viewed from the rear, the top falls to the left.
The red dot on the front edge represents a small part of the top, and it is moving left to right at high speed. The blue dot on the rear edge of the top is also moving left to right at high speed, when viewed from the rear. Any object that is moving at high speed left to right will continue moving left to right due its momentum, although it can also move up or down if an up or down force is exerted while it is moving.
For example, a bullet fired horizontally will continue to move at high speed in a horizontal direction while it falls slowly to the ground under the influence of the vertical gravitational force. Gravity causes the whole top to tip to the right when viewed from the front, but the red dot will tend to move in a straight line since it is moving at high speed. Imagine that the red dot is a small bullet attached to the disk.
The result is that the front edge of the disk lifts upward as the disk falls. The two dashed lines represent the components of the velocity vector — one parallel to the edge of the disk and one perpendicular, showing the front edge lifting up. Similarly, the momentum of the blue dot tends to carry it forward in a straight line.
As a result, the rear edge of the top tilts down. The whole top therefore tilts up at the front edge and down at the rear edge, which means that the top tilts into the page when viewed from the front. That is why the top precesses by moving sideways into the page when it is spinning rather than falling straight down due to gravity. At least, that is how precession gets started when a spinning top starts falling. With steady precession, there is no falling motion at all. The mass of the brass disk is grams, and its diameter is 56 mm. The left end is supported by a length of string.
The axis is slightly above the horizontal since the disk is spinning so fast. It drops below the horizontal as it slows down. The other end bobs up and down rapidly due to nutation. The string swings out from the vertical to provide a centripetal force on the gyro since the gyro rotates slowly in a circular path about the vertical axis.
That is simply amazing. It looks like a magic trick with a hidden spider thread holding up the other end. The torque about the center of mass is directed into the screen in the photo.
The angular momentum of the disk lies along the spin axis and points to the end supported by the string. The change in the angular momentum points into the screen, since that is the direction of the torque, meaning that the tip of the angular momentum vector moves into the screen and the opposite end moves out of the screen towards you. It still looks like magic, especially since the film is viewed in slow motion and the disk seems to be rotating at low speed.
Here is another explanation. The red particle is moving up at velocity v1 and the blue particle at the top is moving into the screen at velocity v1. The disk could rotate out of the screen or it could rotate downwards, which is the intuitive expectation. And vice-versa if the disk rotates downwards. The change in v is directed left to right in each case, as shown in the diagrams below, so there must be a left to right force F on the particle to change its velocity.
The torque is due to the string pulling up on the axle and it acts in a direction into the screen. A horizontal force applied to increase the precession frequency would cause the disk to rise. Here is a gyroscope from www. If the wheel is not spinning then the counter-balance at the opposite end is not heavy enough to hold the wheel up. If the wheel spins, the gyro generates an upward torque to balance the counter-weight, and the gyro precesses slowly. The upward torque is proportional to the precession frequency.
If the support is pushed horizontally to speed up the precession, the gyro rises vertically since the upward torque increases. In , Professor Eric Laithwaite showed that he could lift an 18 kg disk above his head, using one hand, when the disk was spinning on the end of a 0. In Feb , Derek Muller repeated the experiment. The disk acts a gyroscope and precesses in a horizontal plane rather than falling vertically. If the disk was not spinning, it would be impossible to support the disk in that manner.
Note that Derek pushes the axle horizontally at the start to speed up the precession so that the disk rises more easily. If you spin an object on a table, then friction will slow it down until it comes to a stop. A rattleback not only slows down to a stop but it then reverses direction. There are many theoretical papers on the subject and many videos of rattlebacks on YouTube, but there are no simple explanations.
All existing explanations are very mathematical and quite obscure.
Nevertheless, there is a simple explanation, and it involves the effect of friction. You can make your own rattleback by cutting the handle off a plastic spoon and attaching two small masses to each end of the spoon. The secret of a rattleback is that the distribution of mass is not lined up with the geometric axis. So, the two small masses must be located as shown in this 3Mb QuickTime slow motion video taken at fps.
I used two small pieces a Blu-Tack, a re-usable adhesive. If you look carefully you will see that the spoon rocks from side to side and from end to end while it rotates. The sideways rocking motion and the end-to-end motion is correlated rather than being independent. I attached a thin wire to the spoon, along its axis, to see the motion more clearly.
When the spoon tilts sideways, it tends to slip sideways on the the table. The same thing would happen if you tried to balance a pencil on one end on the table and tilted it sideways slightly so that it falls. The bottom end of the pencil would either slide on the table or pivot about the bottom end, depending on the coefficient of friction. Friction acts in the opposite direction to motion of the bottom end. If the pencil pivots about the bottom end, static friction prevents the bottom end from sliding.
The Spinning Tops of Light: Science and Spirituality [Bénédicte Civet-Lobstein] on www.farmersmarketmusic.com *FREE* shipping on qualifying offers. The Spinning Tops are. Light. Science and Spirituality By Bénédicte Civet-Lobstein The Spinning Tops are disembodied beings who coexist with us on Earth in an invisible, parallel.
Now, look carefully at the video. That friction force acts to rotate the spoon in the direction you see it rotating, even if there is no rotation at the start. The spoon therefore has a preferred direction of rotation. If you start it rotating the other way, the spoon will stop rotating and start rocking to conserve energy and it then starts rotating the other way. In the video I started the spoon rocking by pushing down on one end and then releasing the spoon. There was no rotation at the start.