The secret of a rattleback is that the
distribution of mass is not lined up with the geometric axis. Because the spin axis must fall sideways, the torque makes the top fall sideways rather than straight down. :), That's GREAT, Joe! If the strip was also
curved in the sideways direction, like a spoon, it would rotate more freely. If a small mass is located inside a
hollow sphere, then the centre of mass is shifted away from the middle of the
sphere. ;-), As we know: we have the difficulty that the motion cannot even be simplified to 2-dimensional motion; gyroscopic precession is irreducibly motion in all three spatial dimensions. Then note that it takes force to change the direction of spinning (i.e. This is probably the hardest part to explain. The spinning top is pulled in both directions at once so it will actually lean over in a direction half way between the two (draw a diagram if it helps!). Remember, this is trying to explain to a kid without using complicated maths or formal terminalogy. Conclude by asking them the leading question "If nothing is touching or bothering the top, why would the amount of spinning change?". The egg is sliding
rather than rolling on the horizontal surface in this case so there is a relatively
large friction force on the egg. 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. The bottom
end makes a big difference. I used two small pieces a Blu-Tack, a
re-usable adhesive. The
top rotates with \omega much larger than \Omega and tends to roll on the
surface. The red dot on the front edge represents a small part of the top, and it
is moving left to right at high speed. Careful not to catch your nose on the spinning tyre though! 2 Proceed to ask the child to assign a direction to the spinning. If you're Jewish or have a Jewish friend, then chances are you've probably seen or played this fun game that features small objects similar to a spinning top. The outward force of the marbles away from their central axis of rotation would resist this change, thereby causing a resistance to the twisting action on the axis of the wheel. I then asked him to guess what might happen to the marble if the box was pushed in a straight line from left to right. Lote en Mirador del Lago:3.654 m2.Excelente vista al Lago, LOTE EN EL CONDADO DE 1430 m2, EN COSQUIN. This rotates the top in that direction. In order to understand the
behaviour of a spinning egg, it is necessary to understand the effect of the
forces on the egg. Thanks for sharing all the GREAT info, Garcia! The sideways rocking motion and the end-to-end motion is correlated rather than
being independent. Give the child a top and ask them to come up with some way to give a number to describe the spinning. The angular momentum vector L points along the spin axis and rises
slowly as the top rises. Junior employee has made really slow progress. Are Banksy's 2018 Paris murals still visible in Paris and if so, where? Use this line of reasoning (and the analogy) to explain that 5 clockwise around that axis pointing up, can't magically become 5 clockwise around the axis pointing sideways. No one knows exactly how old it is, but it's definitely been around for thousands upon thousands of years. If the disk was not spinning,
it would be impossible to support the disk in that manner. Momentum as an english term is somewhat abstract, imho. In that case, the force on the object is equal to the
rate of change of its momentum. Pretty sure the child's confusion is that why should, I liked you Russian phrase. The spinning top rotates around an unseen principal axis. All existing explanations are very mathematical and
quite obscure. If you're up for a crafty challenge, you can try making your own, Have you ever played dreidel? If the wheel spins, the gyro generates an upward torque to
balance the counter-weight, and the gyro precesses slowly. The other end bobs up and down rapidly due to
nutation. Brass disk on P800
emery paper
at 300 fps. When it's spinning, a top balances on a tiny tip. For an object that's not spinning, all it has is the linear momentum resisting gravity. The promotion of Russian terms is funny, @crasic, but don't you think that the 3-word Russian term is a bit redundant and awkward? 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. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Suppose the mass begins to tip to the right. The egg
precesses about the Z axis due to the vertical force in the Z direction, and it
precesses about the Y axis due to the horizontal force in the Y direction. The red/white sphere has two metal nuts near the middle, screwed onto nylon
thread. At least, that is how precession gets started when a
spinning top starts falling. Dear Peter, be sure that I agree and I know what torque is - but your comments are, in my opinion, not quite appropriate for a nine-year-old, at least not an average one. A rattleback not only
slows down to a stop but it then reverses direction. We're glad you're having fun WONDERing! Some tops are released from about hip level with a snap of the wrist and sent spinning to the floor. A spinning egg is just as amazing. "Which way is up for the top" can lead to this kind of understanding. It is smaller than the spin about the vertical axis. How do I explain why a spinning top doesn't fall down without going into the mathematics of angular momentum? Now imagine the pole is spinning the whole wheel around the vertical axis, similar to a spinning top. Its blue with red. To be honest: I know of angular momentum conservation, but nevertheless every time I play with such a top it is a wonder/riddle to me again. Compared to modern toys, the spinning top may seem quite simple. It precesses once in 1400 frames or in
1400/600 = 2.3 seconds so it precesses at 0.43 Hz or 26 rpm. Ask the child if 5 apples can become 5 oranges magically. Its centre of mass rises slowly
since the brass ball rolls and the friction force at the bottom end is
relatively small. Connect and share knowledge within a single location that is structured and easy to search. If you don't have a dolly with rotatable wheels, you can probably improvise something along these lines. So when gravity makes the top lean over one way, the flipping effect tries to make it lean over in a different direction. All three eggs rise as a result of sliding friction until they start
rolling and then the precession frequency is about the same as the spin
frequency unlike a sharply pointed top where the precession frequency
is much smaller than the spin frequency. If the wheel is not
spinning then the counter-balance at the opposite end is not heavy enough to
hold the wheel up. Also shown are two spherical tippe tops. How to explain gyroscopic precession in a more intuitional way? There are many theoretical
papers on the subject and many videos of rattlebacks on YouTube, but there are
no simple explanations. Warning: I'm gonna play fast and loose with my terminology, and use the word "force" when "impulse" or "torque" or something else might be more appropriate. Undefined behavior (according to clang -fsanitize=integer) on libstdc++ std::random due to negative index on Mersenne Twister engine, Convert all small words (2-3 characters) to upper case with awk or sed. The best answers are voted up and rise to the top, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company. the Wonder of the Day via email or SMS. The torque has a component due to the normal reaction force N in
the vertical direction (N = Mg) and it has components due to the horizontal
friction force F acting at the contact point P. (a) The
top rotates with \omega much larger than \Omega and tends to roll on the
surface. The axis is slightly
above the horizontal since the disk is spinning so fast. Elementary explanation for motion of a gyroscope, Explaining to a five year old - why don't bubbles run like water. Mhhhhm, do You know it Yourself? Besides, some adults DO play with
spinning tops (check the web), and some make very elegant ones (see www.puccimanuli.com under spinners). @Qmechanic Actually the first is not outlandish, as in my experience volunteering at my daughter's primary school "science room", when you try to explain these ideas with a bicycle wheel, precession is the first thing small children almost universally notice after they notice that the wheel doesn't fall over. After a theoretical discussion it is good to have a physical demonstration - Lubos's suggestion of using a bycicle wheel is perhaps the easiest way to demonstrate the fact that "things want to keep spinning the same direction* in a way that the child can feel. The
usual tippe top has a peg on top to spin it, and its centre of mass is located
below the centre of curvature. How to fake a USB flash drive's capacity? LOTE EN VA PARQUE SIQUIMAN A 2 CUADRAS DE LAGO SAN ROQUE. Then note that it takes force to stop it from spinning. The effect is shown in the
following slow motion video clip. It turns itself
completely upside down and ends up spinning with its peg underneath the sphere
that was originally spinning underneath
the peg used to spin it. When you spin a top into motion, you're applying a force that converts the top's potential (stored) energy into kinetic energy, or energy of motion. 51(12),
544-545 (2013) for further details. I am of the opinion that self-discovery is always better than lecture or explanation, so I try to facilitate the child coming to the conclusion (through leading questions and hints) rather than just telling them the answer. Presumably they will come up with something akin to angular velocity, the number of rotations in some time, etc. Most tops are put into motion by twisting the top stem with a snap and releasing. What causes certain spinning tops to flip? 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. Help spread the wonder of families learning together. When it's spinning, you have the linear momentum AND the angular momentum resisting gravity. EXCELENTE OPORTUNIDAD DEPARTAMENTO CNTRICO EN COSQUIN, OPORTUNIDAD CHALET VILLA MIRADOR DEL LAGO. In general bicycle physics is much weirder than gyroscopic physics, with lots of parameters which make things very difficult. :), That's WONDERful, Rose! Now imagine a dot on the outer edge of the spinning top, and another dot halfway toward the center. If spun fast enough, a spinning top will rise to a vertical position
and happily stay there, despite the fact that it will fall over if it stops
spinning. A spinning top is not just a
childs toy. To learn more, check out. In Czech, we say "hybnost" - movability, also translated - but in a bio context - as motility. Hi, Xander! Bangalore? The
effect is described as precession, and is explained in simple terms below. How is Number Of Confirmations derived for a transaction? It's possible that the first spinning top toy was nothing more than an acorn put into motion by a curious kid. The result is that the direction in which the top leans constantly changes - it is pulled around in a circle! So a good explanation would put the two together. the direction of the angular momentum vector). Without getting into advanced physics and mathematics, let's take a look at some of the basic forces that make a top spin. Forgive me for answering my own question, but with some inspiration from the other answers here and some child like thought I believe I have found a great way to help my son gain an intuitive understanding of why spinning tops don't fall over. 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. There is no such torque acting
on the disk, so this cant happen unless a horizontal force is applied
to the axle in an attempt to reduce the precession frequency. The tops were filmed at 300 fps to measure their
spin and rate of precession. I think that science in English would be easier to convey if we had used English translations of the words used in mediaeval / early modern scientific discourse in latin rather than keeping the latin words (German and Dutch are also good at native translations: German sometimes uses Bewegungsgre or Bewegungsmenge = "amount of movement"). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The
only forces on the egg are gravity, the normal reaction force and friction, but
all three videos contain some surprises. (The young scientist version). Here's the clever part! When a spinning top starts to wobble and then falls over, that is because torque starts to pull on the bottom of the top as its spinning slows. The brass end top takes a while to stand up
straight, as shown in the fourth video clip. First, note that it takes force to get the wheel spinning. Is it possible to understand the Gyroscope Effect Intuitively? That is how the two Fs are acting when the disk
rotates out of the screen. If you add up these two independent movements, you find that the the vertical movements (turning up, falling down) have cancelled out, so that its net movement is more akin to rolling. I thought the following post would help, but the answers would just bamboozle him I'm afraid. Imagine that the red dot is a
small bullet attached to the disk. If it is spinning then it does something else. We're glad you liked this Wonder! :), Hi, Dylan! How can I explain or demonstrate the Lorentz Force to a 12 year old? The left end is supported by a length of string. They cover a lot of vector calculus and confuse the hell out of students without ever coming back to this simple intuitive concept. Vancouver? The green sphere has a small piece of blu-tak in the bottom. My nine year old son asked me this very question when playing with his "Battle Strikers" set. Faced by the same question and a background that includes courses in vector calculus, I have sought a simpler answer.
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