30 Sep 10
2 edits
http://www.newscientist.com/article/dn19514-levitating-graphene-is-fastestspinning-object-ever.html
They got 1 micron sized graphene layers to spin at 60 million RPM and they said it was strong enough to be able to be spun up to something like 60 BILLION RPM! They did it optically, like those little black and white vanes inside the vacuum bulb you see at kids science stores, where light hitting the vanes causes the assembly to spin. In the case of the graphene, they use circularly polarized light.
BTW, 60,000,000 RPM is one million revolutions per SECOND!
The graphene is going, 1 million revs per second. Is that all you got, punk?
30 Sep 10
Originally posted by sonhouseWhat will the G-force be?
http://www.newscientist.com/article/dn19514-levitating-graphene-is-fastestspinning-object-ever.html
They got 1 micron sized graphene layers to spin at 60 million RPM and they said it was strong enough to be able to be spun up to something like 60 BILLION RPM! They did it optically, like those little black and white vanes inside the vacuum bulb you see at ...[text shortened]... ions per SECOND!
The graphene is going, 1 million revs per second. Is that all you got, punk?
30 Sep 10
Originally posted by joe shmoNo no, take it as a puzzle if you want.
don't you start.
😵
What will the forces involved be? If you can get it to spin at 60 MC, you can easily with the right method let it spin faster. Unless the forces rip it apart.
So what G-force is there in such a high velocity spin?
- Joined
- 10 Dec 06
- Moves
- 8528
30 Sep 10
1 edit
Originally posted by FabianFnasThere are several forces at work in the problem, none of which can be solved for given the OP, as far as I can tell.
No no, take it as a puzzle if you want.
What will the forces involved be? If you can get it to spin at 60 MC, you can easily with the right method let it spin faster. Unless the forces rip it apart.
So what G-force is there in such a high velocity spin?
Are we talking about the force required to spin the disk up to those speeds? Assuming the force is constant; acts on the body perpendicular to the the axis of rotation; and applied such that torque is maximized, we still need the radius(which we could subseqently determine the mass from), and the angular acceleration of the disk up to the time when it reaches the mentioned angular velocity.
or are we talking about forces at work loading the material which act perpendicular to the axis of rotation but through it? All variables mentioned above need to be specified for this situation as well. However for this Force angular accleration can be 0 (in the other case it cannot ) but the force is still partially a function of the radius (which is not stated)
30 Sep 10
Originally posted by joe shmoYou're right. There are a lot of information missing here in order to calculate the forces involved.
There are several forces at work in the problem, none of which can be solved for given the OP, as far as I can tell.
Are we talking about the force required to spin the disk up to those speeds? Assuming the force is constant; acts on the body perpendicular to the the axis of rotation; and applied such that torque is maximized, we still need the radius(w ...[text shortened]... case it cannot ) but the force is still partially a function of the radius (which is not stated)
So this mean that I'm not impressed by the 60 MC number. I don't know if it's very hard to make a helium nucleus spin at 60 MC or not. But when you start to spin it, I can imagine that there are no upper limits how fast you can spin this helium nucleus. Perhaps there is a limit, but in that case it must be far beyond 60 MC anyway.
But if you begin to rotate a macro object, then we have a peripherum velocity that will tear the object in pieces far less than 60 MC.
So it all boils down to the missing information. Without it, I'm not particularly impressed. It's just a number, not more.
30 Sep 10
1 edit
Originally posted by joe shmoThe radius is about 1 micron, they mentioned micron sized layers so you can assume 1 micron as radius, which would be close enough for government work. Micron sized diameters so if you assume 2 microns then you get a 1 micron radius.
There are several forces at work in the problem, none of which can be solved for given the OP, as far as I can tell.
Are we talking about the force required to spin the disk up to those speeds? Assuming the force is constant; acts on the body perpendicular to the the axis of rotation; and applied such that torque is maximized, we still need the radius(w ...[text shortened]... case it cannot ) but the force is still partially a function of the radius (which is not stated)
Since the layers are just self bound carbon atoms, you can find the mass of one carbon atom and figure the force generated on it using the mass obtained maybe from the periodic table.
- Joined
- 18 Jan 07
- Moves
- 12477
01 Oct 10
1 edit
Originally posted by sonhousePoint of order: in the case of the vacuum bulb thing, it's not the light that does it. Photons in sunlight quantities are much too weak to propel a metal vane of that size. Also, it's not a vacuum inside, it's just sealed tight against any possible air currents. It's the thermal difference between the sides (and resulting air pressure difference) which makes those vanes turn.
They got 1 micron sized graphene layers to spin at 60 million RPM and they said it was strong enough to be able to be spun up to something like 60 BILLION RPM! They did it optically, like those little black and white vanes inside the vacuum bulb you see at kids science stores, where light hitting the vanes causes the assembly to spin. In the case of the graphene, they use circularly polarized light.
Of course, those things aren't micrometer-sized, so this doesn't contradict the graphene experiment.
Richard
01 Oct 10
Originally posted by Shallow BlueDo you know the name of that device?
Point of order: in the case of the vacuum bulb thing, it's not the light that does it. Photons in sunlight quantities are much too weak to propel a metal vane of that size. Also, it's not a vacuum inside, it's just sealed tight against any possible air currents. It's the thermal difference between the sides (and resulting air pressure difference) which ...[text shortened]... gs aren't micrometer-sized, so this doesn't contradict the graphene experiment.
Richard
01 Oct 10
Originally posted by Shallow BlueWe were always told it was a result of it emitting heat on the black side or something like that. This is the first time I heard it had to do with air pressures. Does this mean our teachers had it wrong?
Point of order: in the case of the vacuum bulb thing, it's not the light that does it. Photons in sunlight quantities are much too weak to propel a metal vane of that size. Also, it's not a vacuum inside, it's just sealed tight against any possible air currents. It's the thermal difference between the sides (and resulting air pressure difference) which ...[text shortened]... gs aren't micrometer-sized, so this doesn't contradict the graphene experiment.
Richard
01 Oct 10
1 edit
Originally posted by sonhousehttp://en.wikipedia.org/wiki/Crookes_radiometer
Do you know the name of that device?
From Wikipedia:
They come in various forms, such as the one pictured, and are often used in science museums to illustrate "radiation pressure" – a scientific principle that they do not in fact demonstrate.
01 Oct 10
Originally posted by twhiteheadNice article, I and a bunch of other people had it wrong! I wonder what amount of light intensity would cause the vanes to rotate in a very good vacuum, like 10-7 torr, a typical vacuum we use in ion implanters?
http://en.wikipedia.org/wiki/Crookes_radiometer
From Wikipedia:They come in various forms, such as the one pictured, and are often used in science museums to illustrate "radiation pressure" – a scientific principle that they do not in fact demonstrate.
But back to the g force of the rotating graphene, anyone do that yet?
- Joined
- 10 Dec 06
- Moves
- 8528
01 Oct 10
1 edit
Originally posted by sonhouseyeah, its experiencing large internal forces(on the order of 2E5 Newtons) spinning at that angular velocity ( assuming a mechanical model) which im under the impression is a bad model for bodies of this size, but I dont know any other models so....who knows, It could be very incorrect?
Nice article, I and a bunch of other people had it wrong! I wonder what amount of light intensity would cause the vanes to rotate in a very good vacuum, like 10-7 torr, a typical vacuum we use in ion implanters?
But back to the g force of the rotating graphene, anyone do that yet?
I will note that the modulus of elasticity for the material is very high (.5TPa) according to Wiki.
But doing macro strength analysis at mico levels is not going to be a good model.
Essentially if the forces required to break the interatomic bonds of the lattice stucture are less than the 2E5 number, than the mechanical model was a bust. If noone comes up with this I'll ask my Materials Prof. on monday.
02 Oct 10
1 edit
Originally posted by joe shmoRemember, in the article, they said the graphene could spin a thousand times faster and still not fly apart so whatever the limit is, at a million revolutions per second is nowhere near the limit of mechanical strength.
yeah, its experiencing large internal forces(on the order of 2E5 Newtons) spinning at that angular velocity ( assuming a mechanical model) which im under the impression is a bad model for bodies of this size, but I dont know any other models so....who knows, It could be very incorrect?
I will note that the modulus of elasticity for the material is very ...[text shortened]... echanical model was a bust. If noone comes up with this I'll ask my Materials Prof. on monday.
Of course it is obvious there would be a maximum size sheet that could be spun up to that kind of violent RPM's.