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Quote from: Jaaanosik on 20/04/2020 21:56:33Yes!All right, good. Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?In regards to your question about the CD players: he did give them angular momentum. Pushing an object off-center results in a transfer of angular momentum.In regards to your question about the cat, the total angular momentum is unchanged. The total angular momentum starts at zero and ends at zero. The cat did not generate any net angular momentum. If you actually paid attention to the very video you posted, you would realize that.
Yes!
...In regards to your question about the CD players: he did give them angular momentum. Pushing an object off-center results in a transfer of angular momentum....
Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?
It would be nice if you would be respectful enough to stop skipping over my questions. This is a give and take. You can't expect me to keep answering your questions if you won't answer mine in return. If you answer this question:Quote from: Kryptid on 20/04/2020 22:03:55Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?Then I will answer yours.
.....All right, good. Then here is the next question: do you agree that, before the ship's engine is turned on, the total linear and angular momentum of a stationary ship is also zero?...
Yes, agreed,
Kryptid,I am paying attention to the video I posted. This is digging deeper.It is very import, we have to settle this.Cat started with zero angular momentum, generated half a turn and stopped the rotation, ended up with zero angular momentum again.Where did the NET half turn come from?Jano
Kryptid,what transfer you are talking about?I thought you were saying a linear momentum is a linear momentum and it does not have an angular momentum.I thought you were saying the linear momentum cannot be converted to angular momentum.Jano
Quote from: Jaaanosik on 21/04/2020 16:29:39Yes, agreed,Okay then, thank you. Since we are in agreement that the ship starts out with zero linear momentum and zero angular momentum, we know that the total momentum of the system starts out at zero. If this is the case, then do you also agree that, in accordance with the conservation of momentum, the total momentum of the ship at the end of stroke one must also be zero?...
...Quote from: Jaaanosik on 21/04/2020 15:23:03Kryptid,I am paying attention to the video I posted. This is digging deeper.It is very import, we have to settle this.Cat started with zero angular momentum, generated half a turn and stopped the rotation, ended up with zero angular momentum again.Where did the NET half turn come from?JanoNet angular momentum is not required in order to perform a turn. The solution to the problem is explained at about minute four in the video you linked. For more information, Wikipedia has an article explaining it as well: https://en.wikipedia.org/wiki/Falling_cat_problem...
...They are separate quantities. I'm actually rather amazed that you didn't pick up the solution from the very video you linked earlier from Khan Academy. It explained that the ball hitting the paddle has angular momentum because it is hitting off of the axis' center. It stated that there would be no angular momentum if the ball hit exactly on the axis, despite the fact that the ball has identical linear momentum in both cases. It's exactly the same scenario with pushing the CD player. A force pushing off-center applies angular momentum.
No, because release of potential energy changes boundaries/dynamics of the system.
You hold a kilo in front of you in your hand - momentum zero, you let it go and the momentum is not zero.
A release of potential energy can change arrangement of inertial forces that can lead to conversion/transfer between linear and angular momentum.
can cat turn around without releasing a potential energy?
Where is the change of 0 angular momentum to some angular momentum to 0 angular momentum coming from?
potential energy - angular momentumkinetic energy - linear momentum
When the CD players are ON then the center of mass moves on a chaotic trajectory, forward, sideways, up, down, backwards, ...
A part of the original linear momentum/kinetic energy will be spent on climbing from the potential well so not all momentum/energy generates the forward and rotational motion,
Can we say the original linear momentum is split into the new linear momentum plus the new angular momentum?
Quote from: Jaaanosik on 21/04/2020 17:12:37No, because release of potential energy changes boundaries/dynamics of the system.No it doesn't. That would violate conservation of momentum. A closed system cannot experience a change in net momentum. Period. That's not debatable.Quote from: Jaaanosik on 21/04/2020 17:12:37You hold a kilo in front of you in your hand - momentum zero, you let it go and the momentum is not zero.The momentum is still zero because the Earth is pulled up towards the kilogram with just as much force as the kilogram is pulled down towards the Earth. The momentum of the Earth becomes equal and opposite to the momentum of the kilogram. So the total momentum is unchanged....
Please, tell me where are you going to draw the boundaries of a closed system?
...Second of all, your ship starts off with neither linear nor angular momentum. So the ability to convert one into the other would not make the engine work either. You can't get any linear momentum from angular momentum because there isn't any angular momentum present to work with....
A loaded spring, potential energy, can start a rotation of a wheel, angular momentum
Are you saying this cannot happen??
One of the most powerful laws in physics is the law of momentum conservation. The law of momentum conservation can be stated as follows.For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.The above statement tells us that the total momentum of a collection of objects (a system) is conserved - that is, the total amount of momentum is a constant or unchanging value.
...It can happen. The problem is that you are considering various parts of the system in isolation and not taking into account that momentum (angular or otherwise) is not a one-way street. Newton's third law will cause any donation of momentum to be counteracted by an equal amount of momentum in the opposite direction....
What is causing the wobble of the CD players when they are ON and when they receive gentle external impulse?Where is the action and counter-reaction coming from?Jano
A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed.
Thus, in the absence of an external impulse, the linear momentum of a system remains unchanged.
What is a closed system?From https://en.wikipedia.org/wiki/Closed_systemQuoteA closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed. The cat burning potential energy is losing atoms, mass is getting out of the system.The rotating cat is not a closed system.Jano
Quote from: Jaaanosik on 22/04/2020 01:28:24What is a closed system?From https://en.wikipedia.org/wiki/Closed_systemQuoteA closed system is a physical system that does not allow certain types of transfers (such as transfer of mass in or out of the system), though the transfer of energy is allowed. The cat burning potential energy is losing atoms, mass is getting out of the system.The rotating cat is not a closed system.JanoThat didn't answer my question, now did it?