I know exactly what he was talking about. He is wrong. Yoyos of the same mass do not necessarily play the same speed.
Why?
The comment about wasted string was an aside, and I clearly stated as such… it had nothing to do with the real issue at hand, but it did relate to how fast a yoyo gets down the string, so I mentioned it as a factor, though not one really related to what we were actually discussing.
Anyway, back to the matter at hand.
Re-reading my original post, it isn’t all that clear… so let’s start over a bit.
We need to clarify some terms here and use them consistently, or this is going to be a massive confusing mess to both us and everybody reading it.
Let’s go with RPM = speed of spin. Speed = how quickly you can make the yo-yo move along its plane after the throw. Float (I really, really hate this term) = how quickly a yo-yo responds to your input.
Once at the end of the tether, two yoyos of the same dimensions but different weight distributions, will be different RPMs. As well established, the one with more rim weight will be spinning more slowly… but it will also be more resistant to change.
Your argument, as I understand it, is that within the same plane the yo-yos will move at the same speed along that plane as you play with the yo-yo.
If that is in fact the case, why does any yo-yo feel any different from any other yo-yo of the same weight? A -ton- of yo-yos fall between 64-66g and I’m pretty sure everybody can agree there is a massive variable in how they all feel. Why does one yo-yo play “floatier” than another? (or stated another way, why does one respond to input faster?)
Lower RPM objects are harder to move along their path than higher RPM objects… so RPM does make a difference in the ‘speed’ of a yo-yo… and RPM is determined by rim weight.
Kyle
p.s. yes, I’ve been making yo-yos a long time, and I’ve spent a lot of time on the math of them… that doesn’t automatically make me right about everything, and I’m always open for discussion.
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To add to my previous post, took me a minute to find this.
This is a demonstration of how RPM impacts an object along its path… read don watson’s book on gyroscopic precession as it relates to yo-yos directly.
YES, I know this isn’t ‘exactly’ what we’re talking about, but it demonstrates a similar idea.
I dont need to have an aadvanced understanding of the physics behind it to know tthat I’ve played hundreds of yoyos with similar weights that play at entirely different “speeds”.
Care to state what you think about my question regarding a chopped up Genesis? Im thinking that’s a pretty solid example of what you and Greg are saying. Its the exact same mass redistributed inside the cup, but its definitely not gonna play the same on the string.
Mikers, dunno why you’re getting so vehement about it. 
I’m pretty sure Kyo and I are both the kinds of guy who will admit to being wrong, generally grudgingly. But for both of us it would take considerable arguments to sway the perspective. Not just “I can feel it, can’t you?”. Not good enough for me, and I don’t think it’s good enough for Kyle, ither.
People are adding too many variables and perceptions to the limited and simple part of the equation that I’m talking about… deep breath
I’m not saying two yoyos of the same mass “play the same”. How a yoyo plays is largely a matter of subjectivity. And there are more factors at play than you would think. For example, how quickly a yoyo reaches the end of the string (therefore having enough momentum to go right into a fast trick without more effort!) or if it does so gracefully (the absence of a “thunk”) and encourages you to simply continue with that graceful feeling… The degree to which it is stable (or not) will also affect your approach to that yoyo. It’s way easier to hammer at “fast” tricks when you don’t have to fear tilting out. The feel in-hand or on the catch. All these factors PLUS the aesthetic appeal of a yoyo greatly contribute to your overall feelings for the yoyo, and we invest more emotion into material things than we’d care to admit in an allegedly rational discussion. There are simply some yoyos that you think of as your “fast” yoyos and you play them fast. There are some that you think of as your “chill out” yoyos and you play them chilled out.
The empirical weight of the yoyo usually factors in less than your subjective attitude toward that yoyo. We’ve all experienced it and I think most of us will admit that it’s true. WHen a yoyo that’s on the lighter side happens to coincide with a yoyo that you have a “fast” approach to… well now you’re really playing with lightning.
However: I’m not talking about those things. I’m talking about two yoyos already at the end of tethers, with the same dimensions (mass, diameter, width-- really it’s the mass that matters, but let’s get rid of any unecessary variables) but with different “weight distribution”.
It takes the same amount of force to change the direction of those two yoyos. Period.
They surely have different moments of inertia for the spin (something Kyle actually helped illustrate to me not that long ago!). But people accidentally think that a yoyo just has “a moment of inertia” and apply it to other shifts in motion. That’s not the case. Having the same dimensions and mass, the two yoyos have the same moment of inertia for going around a pivot or snapping to the opposite direction (ie direction changes along the plane I’m referring to… the one we typically play on). It’s a simple factor though I’ve over-explained it. I don’t see how anyone can debate it. Higher RPMs on a yoyo will create more stability (naturally), but that stability doesn’t impact the kind of direction change that is being referenced for “fast” yoyos. Be that as it may, I feel it’s a separate debate. For the sake of MY argument, let’s just assume that the RPMs are the same on both yoyos.
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I’m afraid the video does not actually demonstrate the principles we’re talking about. It’s not the same model and the movements are happening along different planes. Spin up a pair of 50-lb discs and try lifting them with a cord affixed to the middle…it’s going to feel exactly like you’re lifting 100 lbs. Try swinging them… it’ll take some time to get going, but you can do it. Now change each disc’s weight distribution. It will feel like you’re lifting 100 lbs still, and it’ll take the same amount of effort to get them swinging to the same amplitude! Do the same thing with the discs not spinning (imagine their precession is controlled somehow) and your results will be the same.
The model in the video informs the stability and precession discussion (gyroscopic effects), but not change in direction along the plane.
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This is the primary flaw in your argument. You are assuming that the RPM will be the same for two yoyos with different moments of inertia (and all other variables being equal). Kyo clearly demonstrates that the RPM of the two yoyos will be different after identical throws. Yes, you could create a situation in which the RPM of the two yoyos is the same, but that situation is an unreasonable comparison because in the real world people are going to compare the two yoyos immediately after throwing them.
The most important movement of a yoyos on the end of the string is that of translational motion. Normally we would think that translational motion is dependent only on the inertial mass of the object. Kyo then brought in evidence that for a spinning object, translational motion also depends on the RPM of the object.
In a realistic situation where two yoyos are thrown, RPM is dependent on the moment of inertia. Translational motion is dependent on RPM. Therefore, translational motion is dependent on the moment of inertia.
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It’s not MY flaw. It’s the flaw of anyone who wants to conflate two arguments. The argument was whether weight distribution inherently affects the speed at which a mass can change direction.
Whether RPM has an impact on this or not I have my doubts. But again, there’s no such thing as “a yoyo with a different moment of inertia” because that term can be applied to a staggering number of translations. There is no such single property with that name that you can attribute to a yoyo. And people tend to conflate the multiple moments of inertia of a yoyo in motion. I do not actually see the evidence that the translation in question is affected at all by the RPM, but it is irrelevant to my argument.
In essence, what you’re saying is that the moment of intertia of a yoyo spinning up depends on weight distribution. This is an indisputable fact. Then you are proposing that because of this fact, a yoyo thrown with the same force along the same tether with a hypothetically identical bind would produce spins of different RPMs. I am thrilled to agree with this.
But the net result is that the argument becomes “RPMs affect float”, which I am inclined to disagree with but which is not the argument I proposed. My argument was that all things being equal except for weight distribution (including mainly mass), translating from one direction to another along the same plane requires the exact same amount of force. In fact, I am disinclined to even talk about RPMs at all and I only proposed making them equal to emphasize that it’s not my argument and let’s just forget about it. As soon as you are talking about RPMs you are talking about something other than MY (hence the capital letters) argument.
If you’re interested in a second separate debate, though, I’m game. What would make you think that spin will affect the kind of translation of direction that’s under discussion? I don’t have the equipment for this test, but let’s just imagine for a second: you’re got two identical yoyos (forget about weight distribution for a moment), one spinning at high RPM and the other not. If you have a machine that can “tug” the yoyo up (direction change) at the same speed and with the same force, do you believe that they will both jump up to different heights or return to the end of the tether at different times? If you think RPM are a factor, then the answer has to be “yes”. Is that your answer?
Now take two yoyos that are identical except for weight distribution, spin them up to the same speed, and then run the tug test. What are your predicted results? Will one in fact jump more slowly or descent more slowly (“floating”)?
Same two yoyos, spinning at different rates. Otherwise the same test. Which one takes longer before it returns to the end of the tether?
I need to develop a better working knowledge of physics. I know that. But I have enough general intelligence to understand when models refer to one another and when they don’t. And the moment of inertia as it applies to the yoyo being thrown down (and generating RPMs) is not the same as that of translating the yoyo from one set of coordinates to another along the same plane as the spin direction.
I’m just imagining the rush of people fighting for the maximum possible RPM on their throw so that the yoyo can be faster or float more.
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Mrcnja and kyo, by your logic, if a yo-yo is spinning fast enough it will float in mid-air or gently fall like a feather. The equal force of gravity on two objects of equal mass would somehow not cause the same acceleration downward!
The bad link in mrcnja’s chain in the last paragraph is “Translational motion is dependent on RPM.” That video was not about translation, it was about the effect of his hand’s upward force and the downward force of the disc’s weight adding torque on the handle/axis of spin and resulting procession and its effects. The follow-up video about his weight on the scale actually disproves the point mrcnja and kyo are trying to make.
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When people use “float” no one actually means defying newton. Kyo never said any such thing. He is talking about ease of changing the direction of the yoyo.
Gravity is just a directional force. Whether you’re applying a force by swinging the yoyo around or letting gravity do its job, the same principles will apply but on a different scale. Scale ultimately doesn’t matter, though… the math is the same to add 0.0000001 and 0.0000001 as it is to add 1 and 1.
But that’s getting sidetracked. I will grant for a moment that we’re not talking about defying Newton and are strictly talking about changing direction by applying force to a tether. The amount of spin does not affect this type of translation.
There are any number of examples that we can imagine, but man it becomes difficult to create an experiment… Let’s say you’re holding a dead yoyo by its hubstacks and you give it a throw. Then you spin up the yoyo as fast as you can while holding the hubstacks. Are you claiming that you will be able to throw the yoyo further or that throwing the same distance will require less energy?
And just because I probably SHOULD, I lied and I’m going to bring it back to gravity again. All that is happening is that gravity is exerting a force that is causing a direction change. The mass is what’s important. Not the RPMs and not the distribution of the weight. Shape matters insofar as a wide flat object will meet with air resistance, but we’re not talking about wind resistance… and the assumption is that the yoyos are the same general dimensions except for the weight distribution.
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Let’s also not forget that what’s under discussion is the speed of a yoyo (responsiveness to direction change) and not get bogged down in the mire of defining “float”, which to me is a combination of many factors which DO include the things Kyle is mentioning (moment of inertia on a throw, overall mass, gyroscopic properties).
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Like Greg said, gravity is a force that changes the direction of the yo-yo. A string tug is just another force, except it’s exerted unevenly in time (i.e. shorter and harder) and in any direction you want. An equal force opposite to gravity keeps the yo-yo in the same place during a simple sleeper.
If gravity is indeed a force that changes the direction of the yo-yo, and “speed” is the ease with which a yo-yo can change direction due to outside forces, and if speed is affected by the spinning of the yo-yo (as people are claiming), how can that not imply that Newton’s law of gravity can be defied? I think you might have trouble answering that.
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