# yoyo physics question

i was thinking about why some yoyos feel floaty and some dont, remembering Galileo’s experiment concerning falling objects of equal mass, i started to think that if 2 yoyos have the EXACT same mass but it is distributed differently will they play the same? will one feel “floaty” and the other feel like a rock on a string? i think that in THEORY they should play the same but i could be wrong, anyone else have any thoughts about this?

i wasnt too sure where to put this so ill move it if necessary

The way the weight is distributed changes the way the yoyo spins, so they will probably feel different, but I have no science behind this.

in general 2 yoyos of the same mass will not play the same if it is distributed differently. If an object has an uneven density it changes its moment of inertia which changes how it can spin. Even if 2 yoyos looked exactly the same and had the same mass but different distributions they would essentially play differently.

Exactly!

well my question was more regarding how much hang time it would get if popped into the air and if it felt “floaty or not” but considering gravity will pull them down at the same rate i would think that the weight distribution wouldnt matter in regards to the rate they fall to the ground

they are both subject to the same gravitational force, yes, but the weight distribution effects how we perceive(sp?) that force. If the mass of a yoyo was concentrated at a single point in the center, it would feel less floaty that a yoyo whose mass was evenly distributed even if the masses were the same.

Well, their mass wouldn’t either. A soda can and a tank fall at the same speed, accelerating at 9.8m/s towards the center of the earth.

Yes that’s essentially true but you forgetting effects of air drag which depends on the cross sectional surface area of the object. In terms of yoyos, it’s an issue of mass distribution as to how floaty yoyos feel.

so its more a question of the individuals perception of how fast or slow the yoyo falling

I was wondering about the same thing!

You’re absolutely right about the physics. According to Newton’s second law, the acceleration from a force is equal to that force divided by the mass of the object (a=F/m). Distribution of mass makes no difference.

Different mass distributions act only act differently when you’re applying torque* on your yoyo. The two ways you can do that are by throwing it and binding it (i.e. accelerating or decelerating the spin) or pulling the string at an angle so it rubs up against the sides a little bit (making the yoyo tilt a little bit).

My theory behind floatyness is that it’s actually an illusion. When you play with your yoyo, you get a feel for how you think it’s going act. Really high rim weights make the yoyo harder to torque, so it feels like it’s harder to make it move when you’re throwing it or pulling it at an angle. That makes the yoyo feel heavier than it really is in those situations. In situations when you’re not applying torque, the yoyo might feel mysteriously light and nimble by comparison. Therein, I believe is the illusion of floatyness.

*Forces create torque when they make things rotate. Rotating objects are really cool, so they get their own rules in physics. The torque created by a force is equal to that force times the distance between where the force is applied and the axis around which that force makes the object spin. The acceleration in the yoyo’s spin caused by a torque (it’s angular acceloration) is a function of how heavy different parts of the rotating object are and how far each of those parts is from the center of rotation i.e. the yoyo’s weight distribution.

The point is that weight distribution has nothing to do with how long a yo-yo stays in air, and the wind resistance on a yo-yo falling 3 or 4 feet is negligable.

I have two words for you, sir…

Centripetal force.

nuh uh! centripetal force is uniform and constant so it cancels itself out

That is true but the tension in the string is not the same at all points if you do an around the world type move. The tension is greatest and the bottom and least at the top (conservation of energy) which is what is felt then yoyoing. The centripetal force is felt by the yoyo, we feel tension in the string.

as far as my understandings go, to answer this question

i am pretty sure that the answer is not in gravity, but in acceleration. it takes more energy to lift a hevier yoyo because it has more mass. and F=ma so if you increase the mass then it will take more force to get the same acceleration, thus giving you the fealing of a more or less floaty yoyo.

hope i cleared things up a bit ;D and you can go to Andre if you need to, i think this is what he is going to college for

Aw man, I was looking it the wrong system. When he said centripetal force, I was just thinking about the yoyo spinning around it’s axel. The centripetal force you get when you do around the worlds only depends on the mass of the yoyo, though.

This isn’t the case though. We are debating why yoyos with the same weight feel different.

Oh, well in that case i got nothing. sorry for the misunderstanding

Yes! And that very much depends on where that mass is distributed on the yo-yo. Centripetal force moves energy away from the application’s point of center. This is a very key thought to better understanding what we’re all trying to figure out here.

Even though I don’t yet have the math completed to prove this theory, I suspect that this is the key factor in understanding what makes one throw more “floaty” than another.

Andre’s degree lies in the Biology field. IIRC, his big study interest is in APAs, or something along those lines. I suppose that’s more of a neuroscience, though, but who knows?

Pretty far from physics, although I’m sure he knows his fair share about the subject.

i thought that andre might know because my uncle is a teacher there and he works with andre and my uncle knows his fair share of physics.