It's a shame that hyperphysics doesn't have anything on this cos they're usually a good balance of words and maths (i find the wikipedia entry disappointingly mathematical; i expect a bit of background and discussion) as this is something i discovered as a kid playing with the sky remote.

I used to hold the controller at the base with a thumb and a finger or two, then try to flip it end over end one full flip and catch it in the palm of my hand. I found it really hard, but i eventually worked out that it was because i was imparting some sort of force to it as my wrist twisted because if i added more twist it would do a complete spin on both axes and land nicely, and when i tried less twist it would only do half a turn on that axis.

So then i started to hold it across, with one thumb and a finger (bit like a barre grip for a guitarist) straight across it width ways and gently flip it, and bet people they couldn't do it every time but i could

Physics you say? I say WITCHCRAFT

Looks like childrens TV in 2150

*timeshift

Adding video to channels (Timeshift) - requested by ant.

That wikipedia entry was way too simple in that it doesn't explain boo but the equations. I think it boils down to conservation of (angular) momentum when an object has angular momentum along (3) axes. So far I can't give but a rudimentary explanation. A more simple system that would convey the fundamentals would if you were to hold a spinning bike wheel while sitting in an office chair (that can spin). As you rotate your arms (holding the axis of bicycle tire spin) the angular momentum lost will be gained in the seat you're sitting on (making you spin). Here, watch this doofus and see for yourself...



I don't know if it's more complicated in theory, or just in added dimensions
>>




^dannym3141:

It's a shame that hyperphysics doesn't have anything on this cos they're usually a good balance of words and maths (i find the wikipedia entry disappointingly mathematical; i expect a bit of background and discussion) as this is something i discovered as a kid playing with the sky remote.
I used to hold the controller at the base with a thumb and a finger or two, then try to flip it end over end one full flip and catch it in the palm of my hand. I found it really hard, but i eventually worked out that it was because i was imparting some sort of force to it as my wrist twisted because if i added more twist it would do a complete spin on both axes and land nicely, and when i tried less twist it would only do half a turn on that axis.
So then i started to hold it across, with one thumb and a finger (bit like a barre grip for a guitarist) straight across it width ways and gently flip it, and bet people they couldn't do it every time but i could

>> ^rottenseed:

That wikipedia entry was way too simple in that it doesn't explain boo but the equations. I think it boils down to conservation of (angular) momentum when an object has angular momentum along (3) axes. So far I can't give but a rudimentary explanation. A more simple system that would convey the fundamentals would if you were to hold a spinning bike wheel while sitting in an office chair (that can spin). As you rotate your arms (holding the axis of bicycle tire spin) the angular momentum lost will be gained in the seat you're sitting on (making you spin). Here, watch this doofus and see for yourself...

I don't know if it's more complicated in theory, or just in added dimensions
>>


^dannym3141:
It's a shame that hyperphysics doesn't have anything on this cos they're usually a good balance of words and maths (i find the wikipedia entry disappointingly mathematical; i expect a bit of background and discussion) as this is something i discovered as a kid playing with the sky remote.
I used to hold the controller at the base with a thumb and a finger or two, then try to flip it end over end one full flip and catch it in the palm of my hand. I found it really hard, but i eventually worked out that it was because i was imparting some sort of force to it as my wrist twisted because if i added more twist it would do a complete spin on both axes and land nicely, and when i tried less twist it would only do half a turn on that axis.
So then i started to hold it across, with one thumb and a finger (bit like a barre grip for a guitarist) straight across it width ways and gently flip it, and bet people they couldn't do it every time but i could



You don't lose angular momentum by rotating the wheel. When you hold the bicycle wheel vertically, the angular momentum vector of the system in the axis of you and your seat is 0, as the angular momentum of the wheel is not in that same axis.

When you turn the wheel horizontal, the angular momentum vector is pointing either up or down depending on which way you turn it. So the chair spins in such a way that it sets up an opposing angular momentum vector (ie. by spinning opposite way to the wheel) to make the net ang' mom' 0 in that axis.

I think it is likely to have something to do with the moment of inertia of the object about the 3 different axes, and probably the axis around which it is unstable has the smallest value of angular momentum (don't wish to prove that for the object in the video lol). I would call on the example of my tv remote. I've just tried spinning it around two axes - end over end, and helicoptor wise. The third axis is width ways, and you don't even need maths to intuit that i require less force to spin it width ways; more of the mass is centred towards the axis, and angular momentum is dependant upon mass and the distance of the mass from the axis of rotation.

So if it's got less angular momentum, it will not only require less force to make it rotate (remember i have to use my trick to reduce force imparted on either side of the controller as i toss it), but it also has less resistance (any?) to being spun in that axis whilst already spinning in another.

My theory at least. I have a feeling it's close as that seems to tie in with the maths too. Could just be something that only makes sense mathematically. It's not like anyone's ever explained why fermions can't coexist in the same quantum state to me in anything but maths either.

BTW, for those of you that want to have MORE fun with the math aspect of all of this (if you want to try to figure out for example what equation you'll be using here...) go here: Wikiversity's link for Rigid Body States O' Fun!<---WARNING: LOTS of MATH!

Angular momentum, torque, and a strange geometrical shape with different areas of "spin" make for great WTF moments. I like torque the most though, it always provides the most fun through its various breakdowns in Physics...

I can defiantly see a college professor turning that little video into an impromptu test, "Watch this video: Now, assume that this thing has these dimensions and has this mass, also here are the independent velocities for the different areas (if it's a hard class will add in extra stuff like resistance, etc...)... Go ahead and tell me x, y, and, z...? You have twenty-five minutes.".

I really do like this video though. If I was a High School physics teacher my kids would understand what is happening here before they left my class. Screw honors programs and AP crap. All students deserve a chance to be great at something not just the ones that scored good on their tests in elementary (which in UTAH, this IS THE TRUTH!). Off-topic a bit, but I couldn't help it.

Since everybody's throwing their $.02 at this nonsense, I'll contribute mine: Gimbal Lock anyone?

Four words. Zero Gravity Disco Ball.

don't taunt it