completely bogus demonstration: if you look carefully, you will see that the water in the basin for the first demonstration was completely still - and drained straight down. But for the north and south demonstrations, she poured the water into the basin at one side of the basin - setting up circulation in the basin - and immediately pulled the plug. What she was demonstrating was conservation of angular momentum, not the coriolis effect.

It's weird how he locks the front wheel in place and says "so angular momentum isn't the cause", then goes on to explain that angular momentum helps to prevent the front wheel turning too sharply and so is actually critical in keeping the bike upright.

Maybe watch it again and pay attention? He said nothing of computer simulations....

In an isolated system (our galaxy) where there is angular momentum (the spinning about the galaxies central axis), the angular momentum is conserved (it never stops spinning with respect to how much mass is in it, and how far from the centre that mass is).

The objects floating above and below that central plane are NOT in an angular momentum vector, just simply moving about in a chaotic motion. Given enough time, these objects will collide, cancelling out their non-plane motions.....

None of this was derived from a computer model, but it does show it in practice near the end by using one.

The distinction is important.

It's to do with angular momentum. The explanation begins with rotational mechanics and ends a few months later so i'll leave you to it from there

hyperphysics is a fantastic resource for any level of physics.

I feel like if you have a good grasp of all the concepts involved...gravity, conservation of angular momentum, torque, etc...then this kind of is intuitive. It just takes an understanding of physics as a whole to make the leap. (Then again, maybe that base of understanding makes it not intuitive?)

Ya, there is a group using this visualization to show that "gravity is a lie" so your spidey sense is right on the money. When you get down to it, the motion around the center of the galaxy is inconsequential, the orbit of the planets around the sun would be the same. And the gay spiral bs at the end, well, that is not taking into account the motion of the galaxy through deep space, making the the pattern of our motion through space just look like an oscillating mess, not a spiral. Not to mention we might get ejected when Andromeda smashes into us. In the end, all the mass in our solar system was created with angular momentum around the galactic core, and internally, the system was embedded with angular momentum around the sun.

The cradle is better than the track because it allows for larger weights, where the track would require a denser material or hollow particles; but the track is easier for measuring incoming and outgoing force because on a steady grade, it’s simply a measure of distance, which is easy to capture roughly, even without a camera.

If momentum = velocity*mass, then doubling the velocity will double the momentum. Using the cradle, if you drop a ball from very very close to the first stationary ball, a single ball will move from the other side and move a very very short distance. If you then drop the ball from perpendicular, a single ball will move from the other side, and rise to (nearly) perpendicular. I have seen this much in my own observations. I don't think we need to do any calculations to understand that the impact velocity in the first essay is way less than half the impact velocity in the second essay (we don’t need exact numbers; we just need to know that the impact velocity is more than double). That means we have met your criteria for increasing the momentum to more than that of two balls at the first velocity, yet one ball still comes out.

A mental model to demonstrate my theory of “two particles in = two impacts = two particles out” is to imagine a bit of sponge between the last two balls in a Newton’s cradle. Pull the second ball out (which will push the first ball ahead of it) to a great enough height that the momentum of the outside ball’s impact is enough to completely squeeze the sponge and cause a second impact wave. The second ball would impact measurably later than the first, and before the ejected particle came back. Pretty clearly, two balls will emerge from the other side. This is what I think is happening on a micro scale when two independent balls are dropped together.>> ^oritteropo:

Thanks <img class="smiley" src="http://cdn.videosift.com/cdm/emoticon/smile.gif">
I was actually going to suggest that the first part of the experiment should be fairly easy to replicate, with a track and marbles or ball bearings or similar. Unless you have a constant grade the velocity (and therefore momentum) calculations will be a bit tedious, and it occurs to me that angular momentum may have some effect too, so perhaps a video camera and some marks on the track (or sensors and a microcontroller) to directly measure the velocity just prior to impact would be easier. To confirm or disprove my assertion you want to keep increasing the momentum of impact until it's more than the momentum of a two balls, and see what happens.
There are videos of a Newton's cradle type setup only with different sized balls, I might go looking tonight.
>> ^messenger:
That shoulda been @oritteropo too.

Thanks

I was actually going to suggest that the first part of the experiment should be fairly easy to replicate, with a track and marbles or ball bearings or similar. Unless you have a constant grade the velocity (and therefore momentum) calculations will be a bit tedious, and it occurs to me that angular momentum may have some effect too, so perhaps a video camera and some marks on the track (or sensors and a microcontroller) to directly measure the velocity just prior to impact would be easier. To confirm or disprove my assertion you want to keep increasing the momentum of impact until it's more than the momentum of a two balls, and see what happens.

There are videos of a Newton's cradle type setup only with different sized balls, I might go looking tonight.

p.s. Didn't find that one, but did find a good explanation of the one vs two ball collision issue in Newton's cradle:



Based on that, I wonder if a slowmo of the ball in the original video might've shown that it bounced slightly before coming to rest?
>> ^messenger:

That shoulda been @oritteropo too.

Spot on!

>> ^renatojj:

"It seems a small initial clockwise rotation in this body of water is being amplified by gravitational draining and conservation of angular momentum to become a rapid vortex, suggesting a non-inertial frame of reference."
-- Cat

"It seems a small initial clockwise rotation in this body of water is being amplified by gravitational draining and conservation of angular momentum to become a rapid vortex, suggesting a non-inertial frame of reference."

-- Cat

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.

>> ^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.

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

Wow, god damn, that brake that that machine pulls is nothing short of spectacular. I occasionally do braking mechanisms for industrial machinery, and I am dumbfounded as to how he removed that much angular momentum that quickly. It almost looks like an impact brake, which is easily capible of braking like that but difficult to deal with because it involves using parts that destroy themselves, and have to be replaced

it's just a flywheel...i'd say little assistance is coming from the wind and more is coming from the angular momentum (rotational inertia). I bet it is harder to get started than a conventional rickshaw. If you want to know more check out: http://en.wikipedia.org/wiki/Flywheel