7 ms·
Instead of spin I would be leaning more towards rails on a mountain but this requires more space but should be much more easier on payload
by thekalki 4y ago
Instead of spin I would be leaning more towards rails on a mountain but this requires more space but should be much more easier on payload
- DiggyJohnson 4y agoJust musing from intuition: but could gravity and magnetic rails come close to the potential energy of a spinning system?
- bee_rider 4y agoIs a centrifuge considered to have potential energy, or kinetic energy?
- Symmetry 4y agoKinetic.
- zasdffaa 4y agoThat was a very interesting question to which you gave a very definite answer, but why do you say kinetic? Maybe I don't understand what potential energy is. from wiki <https://en.wikipedia.org/wiki/Potential_energy https://en.wikipedia.org/wiki/Potential_energy> "In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors" but a spinning disc in a vacuum would maintain energy indefinitely, taken as a whole, and the spinning disc is a stress in itself.
- krisoft 4y agoFrom Wiki: https://en.wikipedia.org/wiki/Kinetic_energy https://en.wikipedia.org/wiki/Kinetic_energy "In physics, the kinetic energy of an object is the energy that it possesses due to its motion." The spinning disc has energy because of its movement. If it stops spinning (moving) it has no more energy. That is what people refer to when they say kinetic energy. > In physics, potential energy is the energy held by an object because of its position relative to other objects That would be when you put the disc on a high shelf and it falls on you. > stresses within itself When you take the disk and you bend it into an S-shape and it is trying to spring back. > a spinning disc in a vacuum would maintain energy indefinitely Assuming frictionless bearings perhaps. But what does that have to do with anything? > spinning disc is a stress in itself. Not in the way physicist think about it. On the other hand, watching a spinning disk is full of stress! Just think of the last scene of Inception.
- wolfram74 4y agoTo desphericalize the cow a bit, the spinning disk would have /some/ potential energy associated with the tension the material experiences to keep itself from flying apart, but yeah, I don't think I'd bother keeping track of it most of the time.
- zasdffaa 4y ago>> a spinning disc in a vacuum would maintain energy indefinitely > Assuming frictionless bearings perhaps. But what does that have to do with anything? Thanks for this, let me elaborate. First, yes, magnetically suspended. That given, take a box containing some quantity E of energy in the form of petrol or TNT, whatever. Chemical energy. Next take a box containing aforementioned disk, spinning with an energy also of E. From the outside there is no observable difference if both they are left sitting on a warehouse floor untouched, however the box with E of chemical energy is potential energy, the box with the spinning disk has kinetic energy, according to your definitions. Yet they are indistinguishable from without. That's my puzzle. (I'm being slowposted so replies may take a while)
- krisoft 4y ago> That's my puzzle. Sorry but I don't see the puzzle. Are you expecting some "different things need to be able to be distinguished when left sitting on a warehouse floor inside a box, untouched" principle? > I'm being slowposted so replies may take a while. No worries. And sorry that that happened.
- zasdffaa 4y agoYou can't distinguish the boxes externally (just by looking anyway). Therefore you can't say which one contains kinetic energy (the box with the spinning disk) and contains the potential energy (the box with petrol in it). If you can't distinguish kinetic from potential in this circumstance, does the definition of 'kinetic' and 'potential' have any rigorous meaning? I'm fine if they don't, I'm just trying to understand.
- 4y ago
- bee_rider 4y agoThis is what I thought. My physics is a little rusty so I tried to fit it to a potential energy just based off that comment, haha. Like if we look at the rotating (so, non-inertial) frame of reference, then maybe we could define a potential energy off the centrifugal "force..." but that would be illusionary.
- DiggyJohnson 4y agoSorry, my use of potential was a bit of wordplay on my part. I should have stated my question differently.
- bagels 4y agoIf you have enough mass, and enough change in height, sure. Doesn't mean you have a practical way to use that potential energy though.
- amelius 4y agoWhat if you attach the payload to the projectile with a bungee cord, at exactly the moment it is released?
- blacksmith_tb 4y agoI suspect it'd be hard to find a tether material that could take that kind of force without breaking. There could also be some strange dynamics as the projectile and payload would become like bolas[1]. 1: https://en.wikipedia.org/wiki/Bolas https://en.wikipedia.org/wiki/Bolas
- amelius 4y agoYou're probably right. I would love it if someone could put it in a physics simulator, though.
- thekalki 4y agoYou will loose lot of energy on bungee cord aerodynamics, heat, etc
- amelius 4y agoTrue, but the question is: will the payload suffer less?
- Symmetry 4y agoYeah. With a few kilometers of track you're looking more at a thousand times less acceleration though still more than a human could take. Though emerging from a track kept at a vacuum and slamming into the atmosphere is going to be quite a jerk in any event.
- bodhiandphysics 4y agoYour forgetting the evacuated tube. The issue with rail launch on earth is dealing with the atmosphere
- bagels 4y agoYou'd need an awfully long rail. Where does the energy come from for this idea?
- bagels 4y agoJust for fun, accelerating on a rail to appreciable first stage velocities of 2000 m/s at ~3g (for humans): 60 seconds of acceleration along 60 km of rail