but i think what you're asking is why do we have fairly compact flywheels rather than longer, more extended "tails"? and the answer is probably that it makes more engineering sense. you can increase the angular momentum stored in something by making it "bigger" or by spinning it faster. i imagine it's a lot easier to spin a small flywheel to thousands of rpm than to make a "tail" (spinning at a very low speed) thousands of times larger.
also - unless i missed it - this video doesn't really explain all of it. by itself a cat's tail isn't nearly large enough or rotating fast enough to spin a cat's body. the cat is also very "intelligently" (presumably "designed" through natural selection) doing much of the rotation while in a U shape. that reduces the net angular momentum considerably (the two "arms" of the U effectively cancel).
and, from what i remember elsewhere, they also reduce the amount of rotation needed by rotating to only get one pair of legs perfectly aligned. as long as those touch down first there is a little time (i admit i am not sure it is sufficient) to then rotate the other legs while "holding on" to the ground.
>also - unless i missed it - this video doesn't really explain all of it. by itself a cat's tail isn't nearly large enough or rotating fast enough to spin a cat's body.
There's a whole section where they discuss how it's not the tail at all, and even bobtail cats can land on their feet. So you definitely missed it!
Oh, I can chip in here regarding big vs small flywheels.
If you look at the purpose of a flywheel - ie storing kinetic energy - a bigger/smaller wheel can serve the same purpose. The reason we don't have "large" flywheels is twofold:
1. size (obvious)
2. Torsional/shear stress - most materials are bad at tolerating shear stress. A bigger flywheel would require immense amounts of torque to get it moving. Generating a higher torque would impose huge amounts of torsional stress on the shaft driving the wheel.
but i think what you're asking is why do we have fairly compact flywheels rather than longer, more extended "tails"? and the answer is probably that it makes more engineering sense. you can increase the angular momentum stored in something by making it "bigger" or by spinning it faster. i imagine it's a lot easier to spin a small flywheel to thousands of rpm than to make a "tail" (spinning at a very low speed) thousands of times larger.
also - unless i missed it - this video doesn't really explain all of it. by itself a cat's tail isn't nearly large enough or rotating fast enough to spin a cat's body. the cat is also very "intelligently" (presumably "designed" through natural selection) doing much of the rotation while in a U shape. that reduces the net angular momentum considerably (the two "arms" of the U effectively cancel).
and, from what i remember elsewhere, they also reduce the amount of rotation needed by rotating to only get one pair of legs perfectly aligned. as long as those touch down first there is a little time (i admit i am not sure it is sufficient) to then rotate the other legs while "holding on" to the ground.