a hard-boiled egg is spun fast e

2022.07.31
why does my kitten chew on everything

a hard-boiled egg is spun fast e

If a hard-boiled egg is spun fast enough it will rise up and spin on one end. :). Explaining Newton's Laws of motion to a 6 year old. 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. Thank you for providing a summary of how a toy top spins! Now imagine a dot on the outer edge of the spinning top, and another dot halfway toward the center. @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. Well, the angular momentum conservation is still the essence although it may be formulated in a different language. OK, I'll give it a shot. Pulling in different directions on the top and bottom of the wheel, makes the whole wheel want to flip over. What is the source for C.S. The other end bobs up and down rapidly due to nutation. As it spins in its upright position, it rotates around an invisible vertical axis. It is also an adult toy, in the sense that it helps to have a PhD in physics to figure out how it works. Just like when the wheel is rotated while the pole is spinning, this creates pulls and drags on parts of the spinning top that make it want to flip over in the third direction, at 90 degrees. I might not have recorded the details of the experiment accurately but maybe the BBC archives might have a recording or may be some one could replicate the experiment, record it, and post it on YouTube? 20142022 National Center for Families Learning, http://wonderopolis.org/wonder/what-makes-a-toy-top-spin, National Center for Families Learning (NCFL). I then asked him to imagine a set of boxes, each containing a marble, attached to the circumference of a wheel. Of course energy is used every time the top must lift itself, so it eventually slows down and crashes. There is an even simpler explanation. Tops are never perfectly balanced and weighted. spinning tops drawing disc cutting See Eur J Phys Jan 2018. (c) The tippe top rotates in the opposite direction to the egg (that is, \theta increases) since the sliding friction force is in the opposite direction. Bicycles are constructed so that the point where the extension of the front fork pivot would hit the ground is in front of the point where the front tire hits the ground; the distance is called the "rake". Imagine a wheel mounted on a pole, like this diagram from wikipedia: http://upload.wikimedia.org/wikipedia/commons. First of all, I asked my son to imagine a single marble contained within a box. Imagine a point on the wheel near the outer edge (dm1 on this diagram) and imagine you rotate the wheel to bring this point toward the top. That friction force acts to rotate the spoon in the direction you see it rotating, even if there is no rotation at the start. Now, look carefully at the video. Thanks for sharing all the GREAT info, Garcia! Try reading through this Wonder one more time and see what you discover!! There's another old toy that most children play with at some point in their lives. 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. What happens if a debt is denominated in something that does not have a clear value? Explaining conservation of angular momentum is a good idea. The wheel is mounted vertically and can rotate around a horizontal axis, in addition the pole can spin the wheel around a vertical axis. How many different kinds can you find? The torque about the center of mass is directed into the screen in the photo. All are described by Eulers angular momentum equation which relates the change in angular momentum to the torque on the object. A rattleback not only slows down to a stop but it then reverses direction. My nine year old son asked me this very question when playing with his "Battle Strikers" set. It's going too fast for the smaller circle, so it creates a 'pull' on the wheel, shown by the arrow. You might need to draw a picture or use a model to convey this. It still looks like magic, especially since the film is viewed in slow motion and the disk seems to be rotating at low speed. 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 bottom end makes a big difference. Thats the amazing part. When a spinning top starts to tilt, the point in contact with the supporting surface shifts away from the axis causing the top to roll. There was no rotation at the start. I cant remember what the mathematics was behind this but I knew the boy could easily move the heavy bar up and down. This is a pretty nice yet simple toy in various science museums, including "Techmania" we have here in Pilsen. Some toys have a spinning gear that is activated by pulling a plastic, toothed strip through it to launch the top. How is Number Of Confirmations derived for a transaction? If you have a dolly with rotatable wheels, sit on it and have him push you around. I used two small pieces a Blu-Tack, a re-usable adhesive. Every time gravity tries to pull the top over one way, the flipping effect makes it lean a different way. Now you can show the same thing for points on the bottom half of the wheel, except that the pull and the drag on the bottom half are in the opposite direction to those on the top half. 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. Bicycles will actually correct such perturbations. I told him that scientists like to call this inertia. Now imagine a point at the top of the wheel (dm2) and you rotate the wheel to bring it toward the outer edge. It comes in a wide variety of shapes and colors, but its function remains the same across varieties.

That's a lot of complexity to wrap one's head around. In Czech, we say "hybnost" - movability, also translated - but in a bio context - as motility. LOTE EN VA PARQUE SIQUIMAN A 2 CUADRAS DE LAGO SAN ROQUE.

See Eur J Phys Jan 2018. Here is another explanation. A spinning egg is just as amazing.

Now, thinking about individual atoms within a solid body as tiny little marbles locked within their own tiny little boxes made up of adjacent atoms gives him an intuitive way to appreciate why the spinning top does not fall over. That is how the two Fs are acting when the disk rotates out of the screen. if the top decided to fall, the spinning would either disappear or would be replaced by a totally different spinning around a horizontal axis, and Nature doesn't allow such a change of the amount of spinning to occur quickly. The key here is to appreciate the independence of the marbles axis of rotation from that of the boxes attached to the wheel. 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!). 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 told him that scientists like to call these phenomena rotational inertia and the centrifugal force. How can I explain or demonstrate the Lorentz Force to a 12 year old? If the disk rotated down the screen the two Fs would generate a torque about the vertical axis. The spoon therefore has a preferred direction of rotation. Remember, this is trying to explain to a kid without using complicated maths or formal terminalogy. (b) The egg rotates initially with \Omega much larger than \omega so point P slides out of the page and the sliding friction force on the egg acts into the page. The sideways rocking motion and the end-to-end motion is correlated rather than being independent. 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. They probably have fond memories of slingshots, rubber balls, and battles between groups of tiny green Army men. The way the wheel is spinning means the the circle the dot makes as it gets nearer the top must get smaller, so that part of the wheel has to slow down. Junior employee has made really slow progress. The spinning top is spinning about its vertical axis, like the wheel being spun around by the pole. Along time ago (1960's) I saw on TV a show where a scientist was explaining the working of a spinning top in front of an audience of children. 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. If you don't already have one at home, try to purchase one to take home to play with, so you can see the physical forces you learned about in action. You might also show him that when he spins on a desk chair, his 'speed' changes when he holds h, +1 for the bicycle wheel suggestion. The egg therefore rises. The third and fourth is the same disk supported on a round, brass knob. :), That's GREAT, Joe! What are we talking about? If the top were perfect in every way -- perfectly balanced and weighted -- and the floor was perfectly level as well, the top would rotate pretty much indefinitely.

Friction acts in the opposite direction to motion of the bottom end. If it is spinning then it does something else. Disregarding the term moment you can describe angular momentum (and linear momentum) as an amount of motion, since quantities of things is something a 9 year old should be fairly familiar with, I propose pivoting explanations around this interpretation. It precesses quickly about a vertical axis through the middle of the egg and precesses slowly about a vertical axis located outside the egg. As a result, the rear edge of the top tilts down. If you spin an object on a table, then friction will slow it down until it comes to a stop. Because the spin axis must fall sideways, the torque makes the top fall sideways rather than straight down. Torque can be applied by a snap-twisting motion of fingers, or by pulling a cord wound around the neck of the top. 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? 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 this occurs, the top begins to wobble, demonstrating a scientific principle called precession. :), Hi, Dylan! 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. Lets be practical and think with the mind of 9 year old, this is my approach: Tell him to stretch his arms and start spinning and now tell him to fold his arms and start spinning again (make sure he doesnt do it vigorously ) and now ask his observation saying which one was easy and say the same feeling would have been to the spinning top if it could think , you can then show his feet (compare with the tops axial) and say you are able to spin without falling as you are maintaining your position and speed relative to this point, Hope this will clear your child's doubt :). The axis is slightly above the horizontal since the disk is spinning so fast. Here is a spinning hollow plastic egg, a solid wood egg and a solid aluminum egg. The only forces on the egg are gravity, the normal reaction force and friction, but all three videos contain some surprises. The result is that the direction in which the top leans constantly changes - it is pulled around in a circle! The red/white sphere has two metal nuts near the middle, screwed onto nylon thread. Math Proofs - why are they important and how are they useful? While precession depends on the conservation of angular momentum, I think this explanation makes it clear what's going on kinematically, without relying on concepts that are hard to develop at that age. We're glad you liked this Wonder! So a good explanation would put the two together. A pair of forces is OK for a nine-year-old. ;), I quibble with your mention of "the torque acting on the bottom tip of the top", insofar as the.

Lead them into the right direction by challenging them to more precisely state the direction of the spinning. 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. I'm going to take a stab at this! It also works nicely as a tippe top. Let's say it is going clockwise. Here's the clever part! The pressure applied to the top to start the spinning motion is called torque. When a forward moving bicycle rider starts falling to the right, the wheel turns such as to bring the bicycle underneath the falling rider and it the process restores his position. To really distinguish torque from force, one needs some vector calculus - and cross product. We're glad you liked today's Wonder! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Here is a curved aluminum strip with an offset bolt at each end. When it comes to old toys, the spinning top is really, really old. Whether you spin the top with your fingers or hold the top upright while you pull a string to start it spinning, the top spins rapidly, miraculously staying upright for a long time before eventually beginning to wobble and finally fall back onto its side. (Showing that the angular momentum was zero!). However, that is not the case. As soon as the top starts leaning in a different direction, that becomes the new direction that gravity tries to tip it over in. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Over time, it was probably a natural progression to begin carving pieces of wood into acorn-shaped toys. Twisting the wheel about its axis would effectively pull two sides of the wheel closer to the axis of rotation of the marbles. 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. Your 9-year old son? All four objects here are spinning on a horizontal surface, all precess at angular velocity \Omega about a vertical axis (Z) through the centre of mass (G), and all spin at angular velocity \omega about an axis of symmetry. It precesses at two different frequencies at the same time, about two different vertical axes. Then note that it takes force to stop it from spinning. No formulas required! My answer is much that same as to why one can easily balance on a typical bicycle. This is probably the hardest part to explain. Imagine the top from, well the top. The bottom end of the pencil would either slide on the table or pivot about the bottom end, depending on the coefficient of friction. If the support is pushed horizontally to speed up the precession, the gyro rises vertically since the upward torque increases. Spun slowly clockwise, the egg precesses in a counter-clockwise direction, rocking from one end to the other, in the same way that people move heavy furniture. It looks like a magic trick with a hidden spider thread holding up the other end. 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. In any case, the potential energy within the top is released, changing to kinetic energy, the energy of movement and motion. As long as the top keeps spinning, the flipping effect means it can't fall over! How do I explain why a spinning top doesn't fall down without going into the mathematics of angular momentum? Finally you can use this to explain why the spinning top can't fall over. For that reason, a tippe top stands upright when placed at rest on a horizontal surface. First, you want to get him familiar with the idea of linear momentum. Imagine (or better, draw!) 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. That is simply amazing. At one point near the beginning, the spoon actually slides on the table, but mostly it doesnt because static friction prevents it sliding. 3 Any object weighted on one side will tend to fall to that side when it is allowed to fall. When you think of your favorite childhood toys, what comes to mind? The blue dot on the rear edge of the top is also moving left to right at high speed, when viewed from the rear. 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.

Tidal forces in daily situations: where to find it? The left end is supported by a length of string. Why would you need 3 words to express such a simple idea? Closest equivalent to the Chinese jocular use of (occupational disease): job creates habits that manifest inappropriately outside work.

Personally I consider the Russian equivalent " " (roughly translated as the moment of the amount of motion) to be much more illuminating to a layman. The angular momentum vector L points along the spin axis and rises slowly as the top rises. Dr. Motl's suggestion of a bicycle wheel is a good one. The analogy being that you have a number and a qualifier, apples corresponds to a direction, 5 corresponds to the angular velocity. Why don't spinning tops fall over? It has further to go, so it must go faster in order to get all the way around in the same time. the Wonder of the Day via email or SMS. This was to stimulate his thinking about the reluctance of the marbles to start moving, reluctance to stop moving once they had started and the marbles apparent desire to push outwards from the centre of the wheel. Conclude by asking them the leading question "If nothing is touching or bothering the top, why would the amount of spinning change?". We're glad you're having fun WONDERing! Are Banksy's 2018 Paris murals still visible in Paris and if so, where? The effect is described as precession, and is explained in simple terms below. Give the child a top and ask them to come up with some way to give a number to describe the spinning. The spin axis must move sideways instead of down, but that is just stating the observed facts in fancy technical words. It's GREAT when we're learning and having fun! Lewis' quote "A good book should be entertaining"? We're so glad you joined the discussion, Jessica! 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. Want to add a little wonder to your website?