Kinetic to heat (building a spaceship)
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From: nuny on 12 Jun 2010 08:26 On Jun 10, 12:46 pm, gb <gb6...(a)yahoo.com> wrote: > Usually people want to avoid friction, I want to create one. > > The idea is that there is a spaceship in space. You throw something, a > weight from the front of the spaceship to the back of the spaceship, > then the spaceship moves. > > But when the weight reaches the end of the spaceship, the spaceship > stops in space. > > Now what if we convert kinetic energy into heat? Say, by throwing the weight at something that stops it gradually by inducing drag rather than all-at-once by impact? > Heat is this thing > which can be lost as friction between the weight leaving the top of > the spaceship and arriving to the end. Heat *is* kinetic energy, the energy of motion of molecules and atoms. Look up "phonon". If all the individual velocity vectors of an object's component bits sum to zero in all directions, that's heat. If there's a nonvanishing component, that's velocity. Kevlar projectile-proof fabric works by converting the velocity of projectiles into heat, which deforms the kevlar fibers. Hang a kevlar curtain in the middle of your ship and fling the weight into it; the kevlar gets hot, and the weight stops because the kevlar is anchored to the ship (or it might as well not be there). You are thinking that if the kevlar weren't there, the ship would move a bit and then stop because the impact of the weight in the ship's tail exactly cancels the force of your throw, which is correct according to old-school Newtonian physics. But, with the kevlar in place some of the velocity vector of the weight gets converted to (presumably) perpendicular velocity of the heated kevlar fibers. So, the ship will move a bit, then slow down, but *not stop* since all the momentum didn't cancel, right? Let's tighten those curtain rods so the kevlar is basically a big drumhead, bolted to the ship's hull. Throw the weight and it will bounce, but will come back slower because some of its impact energy got "wasted" warming the kevlar. Presumably, you could keep bouncing the weight off the kevlar, and have a reactionless drive (no exhaust) at the expense of replacing the kevlar when it catches fire or melts too much to stop tossed weights. That what you're thinking? Mark L. Fergerson
From: gb on 13 Jun 2010 17:29 On Jun 11, 6:58 pm, Sam Wormley <sworml...(a)gmail.com> wrote: > On 6/11/10 5:09 PM, gb wrote: > > > Radiation loss (internally lost energy of momentum) may be interesting research, > > but may turn out as illegal as perpetual motion machines. Kinetic energy may > > be impossible to lose away in any form. > > You have missed a very fundamental finding in physics. Momentum > is always conserved! There is no "internally lost energy of momentum" > > You appear not to know the differences between the concepts of > momentum, energy and thermodynamics. Easily remedied with a freshman > level physics textbook. Google is your friend. There is lost absorbed energy. You gang five pool table balls on wires, and you hit one ball and the last one moves. Momentum is there. Now I take away momentum, in that sense of 'internally lost energy of momentum'. I fill plastic bags with water and try the same experiment. Energy gets absorbed. In a way, the water bags are on the bottom of the spaceship, and a ball crashes into these bags. These water bags are levitating and kept loosely in place. The last bag on the bottom touches the bottom of the spaceship like a feather. Even in space momentum (incoming with the ball, transfer of momentum through the balls and the last one moves, can dissipate through absorbing energy.
From: gb on 13 Jun 2010 17:30 On Jun 11, 7:01 pm, Sam Wormley <sworml...(a)gmail.com> wrote: > On 6/11/10 5:20 PM, gb wrote: > > > There are ways with pressure to accelerate something, like hot and > > cold gas. Compressed liquid will immediately turn into gas, and cold > > will accelerate toward hot. The particles slam on the bottom of the > > ship stronger from introduced pressure which accelerates the motion of > > particles. > > > Can use hot and cold difference, or pressure difference. In the end > > the resulting slam at the bottom of the spaceship produces the stop, > > which may be a stronger force than what initially was thrown or > > released downward. > > You cannot fool mother nature. Momentum is conserved in closed > systems. > http://en.wikipedia.org/wiki/Momentum It refers to perpetual motion machines that no such thing can be created. I think in the reverse. I want the worst friction possible to absorb energy. I am not claiming my idea works or can work.
From: Sam Wormley on 13 Jun 2010 17:39 On 6/13/10 4:29 PM, gb wrote: > Now I take away momentum, in that sense of 'internally lost energy of > momentum'. You have missed a very fundamental finding in physics. Momentum is always conserved! There is no "internally lost energy of momentum" You appear not to know the differences between the concepts of momentum, energy and thermodynamics. Easily remedied with a freshman level physics textbook. Google is your friend.
From: gb on 13 Jun 2010 17:40
On Jun 12, 5:26 am, "n...(a)bid.nes" <alien8...(a)gmail.com> wrote: > On Jun 10, 12:46 pm, gb <gb6...(a)yahoo.com> wrote: > > > Usually people want to avoid friction, I want to create one. > > > The idea is that there is a spaceship in space. You throw something, a > > weight from the front of the spaceship to the back of the spaceship, > > then the spaceship moves. > > > But when the weight reaches the end of the spaceship, the spaceship > > stops in space. > > > Now what if we convert kinetic energy into heat? > > Say, by throwing the weight at something that stops it gradually by > inducing drag rather than all-at-once by impact? > > > Heat is this thing > > which can be lost as friction between the weight leaving the top of > > the spaceship and arriving to the end. > > Heat *is* kinetic energy, the energy of motion of molecules and > atoms. Look up "phonon". If all the individual velocity vectors of an > object's component bits sum to zero in all directions, that's heat. If > there's a nonvanishing component, that's velocity. > > Kevlar projectile-proof fabric works by converting the velocity of > projectiles into heat, which deforms the kevlar fibers. Hang a kevlar > curtain in the middle of your ship and fling the weight into it; the > kevlar gets hot, and the weight stops because the kevlar is anchored > to the ship (or it might as well not be there). > > You are thinking that if the kevlar weren't there, the ship would > move a bit and then stop because the impact of the weight in the > ship's tail exactly cancels the force of your throw, which is correct > according to old-school Newtonian physics. But, with the kevlar in > place some of the velocity vector of the weight gets converted to > (presumably) perpendicular velocity of the heated kevlar fibers. So, > the ship will move a bit, then slow down, but *not stop* since all the > momentum didn't cancel, right? > > Let's tighten those curtain rods so the kevlar is basically a big > drumhead, bolted to the ship's hull. Throw the weight and it will > bounce, but will come back slower because some of its impact energy > got "wasted" warming the kevlar. Presumably, you could keep bouncing > the weight off the kevlar, and have a reactionless drive (no exhaust) > at the expense of replacing the kevlar when it catches fire or melts > too much to stop tossed weights. > > That what you're thinking? I brought up a theory: the opposite of perpetual motion machines, in space. What is thrown down from the top of the ship moves the ship up. Simply what I realized, is what if bad friction takes away energy in a way that is lost. I started thinking that energy can be lost through heat, and energy is a thing that can evaporate invisibly. A theory. |