But as the spaceship moves it interacts with the outside. This means that exterior forces are acting on the spaceship so it is no longer a closed system.
I do not need to go into detail to explain the error of your arguments regarding conservation laws and newtonians will be pleased that this thought experiment includes third law as well.
Quote from: chazemz on 09/11/2017 05:31 pmBut as the spaceship moves it interacts with the outside. This means that exterior forces are acting on the spaceship so it is no longer a closed system.So you actually aren't talking about a closed system at all, you are talking about an open system. To describe anything about this system's behavior, you need to define exactly what it is interacting with outside, and what these forces are.Quote from: chazemz on 09/11/2017 05:31 pmI do not need to go into detail to explain the error of your arguments regarding conservation laws and newtonians will be pleased that this thought experiment includes third law as well.Error of what arguments? The only thing I stated is the simple fact that batteries don't store momentum. And yes, you have to respond to arguments if you want to have a conversation.
If you want to go further, take the spaceship into a region of nothing and then fire the cannon. With nothing to interact with, it will remain a closed system. So theoretically speaking you can move a closed system and conserve momentum.
I was not referring to you in the arguments.
Mmmmm, I agree, but is momentum stored energy?
Momentum and energy are not the same thing. Mmmmm, I agree, but is momentum stored energy?
If a spaceship was to be fitted with a device that could move the spaceship from within and the spaceship was to move within the confines of the known universe, as soon as the spaceship begins to move it can no longer be classed as a closed system.
The battery could be described as a rocket engine in that it converts stored chemical energy into kinetic energy.
Quote from: chazemz on 09/12/2017 12:50 pmIf a spaceship was to be fitted with a device that could move the spaceship from within and the spaceship was to move within the confines of the known universe, as soon as the spaceship begins to move it can no longer be classed as a closed system.Not true, the spacecraft moving does not make it an open system. You had correctly mentioned previously that external forces are involved in making it an open system. You have not described any forces though. We are talking about a spacecraft in deep space. There are no forces defined on it, so it is a closed system, unless you describe external forces acting on it.Quote from: chazemz on 09/12/2017 12:50 pmThe battery could be described as a rocket engine in that it converts stored chemical energy into kinetic energy.Momentum conservation says that this doesn't make sense. You can't just convert chemical energy to kinetic energy, you have to balance conservation of momentum by expelling some sort of exhaust.
The rocket engine does it by combustion, the battery would do it by using the flow of electrical energy/power..So Watts = joules = newtons.
You transfer energy from the battery onto the body of the spaceship. In low earth orbit it would then change to an open system.
It would be easier if we could define when a “closed system” is a “closed system” which is what I have tried to do in the earlier posts. If we place a charged battery into the spaceship and close all the hatches, have we got a” closed system”? So another little thought experiment! We take the cannon outside the spaceship and leave a hatch open. We fire the cannon so the cannon ball flies through the hatch and then close the hatch. What have we got?. Technically it is a “closed system” since the cannon ball has not interacted with the spaceship. But we have an “open system” in waiting since we can tell the future and know what is going to happen. And as soon as we define the system as “closed” does the cannon ball become part of the system so cannot be referred to as “exterior”
With reference to the exhaust, I need to know how you define “conserve”Would it not be better to use the term energy/momentum are always “accounted for”?
*snip*With reference to the exhaust, I need to know how you define “conserve”Would it not be better to use the term energy/momentum are always “accounted for”?
You simply have to define what your system is. If you are going to leave the hatch open and let the cannon ball fly out you can either include the cannon ball in the system or not.The cannon ball flies INTO the spaceship, then the hatch is closed.Is it then classed as a "closed system".If it is a "closed system" what will happen to conserve momentum in the system.