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Bobolink,What happens when the Cubli rotates in zero-g?Will the outside frame rotate 45 degrees as in the video if the frame is not attached to anything?Yes, no?Jano
Quote from: Jaaanosik on 23/04/2020 21:31:28Bobolink,What happens when the Cubli rotates in zero-g?Will the outside frame rotate 45 degrees as in the video if the frame is not attached to anything?Yes, no?Janohttps://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ethz.ch/content/dam/ethz/special-interest/mavt/dynamic-systems-n-control/idsc-dam/Research_DAndrea/Cubli/RevisedManuscript.pdf&ved=2ahUKEwiLjYjutP_oAhVFZM0KHcH5DccQFjADegQIBBAB&usg=AOvVaw3Q75p6hREw01NhghV2_P53Here is the paper written by the inventors of the cubli. Sad, to say but the conservation of momentum is kind of the basis for the cubli. But what the heck, why let facts and science get in the way of your fantasy.
....it can generate the angular acceleration also known as torque
Please, don't get fooled by the fact that Cubli is an inverted pendulum in the video.
Quote from: Jaaanosik on 24/04/2020 23:43:46....it can generate the angular acceleration also known as torque Angular acceleration is NOT known as torque Quote from: Jaaanosik on 24/04/2020 23:43:46Please, don't get fooled by the fact that Cubli is an inverted pendulum in the video.No one is getting confused. This device uses conservation of momentum to do what it does. Don’t confuse rotation, inertia, kinetic energy, potential energy, and angular momentum or you will never understand how this and the falling cat work.
I used the term in a 'loose way' to see who is going to pick it up.
Torque is rotational inertia multiplied by the angular acceleration. The relationship is the same as F=ma for the linear systems.
Quote from: Jaaanosik on 25/04/2020 16:12:18I used the term in a 'loose way' to see who is going to pick it up.Yeah, yeah, of course you did By the way, I'm not paying attention, I just skim sample posts to check spamming etcQuote from: Jaaanosik on 25/04/2020 16:12:18Torque is rotational inertia multiplied by the angular acceleration. The relationship is the same as F=ma for the linear systems.yes, we all know these relationships, but I noticed further back you get very confused about quite a few of them.We also know how the device works
Kryptid,can I ask the following question at the physics forum?
Quote from: Jaaanosik on 29/04/2020 21:48:41Kryptid,can I ask the following question at the physics forum?No, keep them here.
is there anything wrong with the question?
Quote from: Jaaanosik on 30/04/2020 02:40:11is there anything wrong with the question?The problem is more with the asker, not as much with the question. Yes, keep it here.The question also has problems. Your description suggests the addition of a force vector to a torque vector, which is adding different things.The answer to the question is trivial: The ISS is moving at over 7 km/s relative to 'ECI', so of course it is going to change its position in this frame regardless of what minor pushes the astronauts and gyros decide to perform. If it were stationary in that frame, it would immediately fall to the ground like any other dropped rock.Secondly, Earth Center (like any real object I can think of) is always accelerating, and thus does not define an inertial frame. For thought experiments that take away other objects like the sun, there is an inertial frame defined by the center of gravity of the full system being considered, but you didn't reference that.
It is time to pause, ... to think, ... to think more, ...
I wanted to have the question real, I did not describe it in the best way.Let us make it unrealistic. The ISS is in the intergalactic space, the ISS center of mass is stationary in the reference frame of the surrounding galaxies. The flat space-time as we can get. The interstellar space-time has too much curvature compared to the intergalactic one.
Let us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).Is the ISS center for mass going to be disturbed (moved out of position) in in the reference frame of the surrounding galaxies?
Quote from: Jaaanosik on 30/04/2020 16:07:53I wanted to have the question real, I did not describe it in the best way.Let us make it unrealistic. The ISS is in the intergalactic space, the ISS center of mass is stationary in the reference frame of the surrounding galaxies. The flat space-time as we can get. The interstellar space-time has too much curvature compared to the intergalactic one.Short story: We're defining a stable environment to keep outside influences from messing with the answer. That's good.QuoteLet us assume an astronaut pushes to the right inside the ISS (the green force vector) and the ISS CMG's compensate with the opposite torque (red arrow).Is the ISS center for mass going to be disturbed (moved out of position) in in the reference frame of the surrounding galaxies?Conservation of momentum says it cannot be disturbed, so that's the easy answer. You've been told this in countless posts but you continue to ignore it all. Hence the discussion staying here in lighter-side.BTW, you're still making the mistake of comparing two vectors of different units. Force and torque cannot compensate for each other.Force/momentum: Astronaut pushes with F for a second, sending astronaut one way and the rest of the ISS the other way. Those balance, both in force and momentum. Astronaut hits the far wall and both stop, and the center of mass has moved not a bit.The gyros have no effect on this.Torque: Astronaut applies torque T for 1 second to the ISS structure and the gyros (which can be anywhere) compensate. Assuming the thing has zero angular momentum before (you didn't specify that), then the angular momentum of the astronaut relative to the system is exactly compensated by the opposite angular momentum now acquired by the gyros, until he hits the far wall and the gyros are forced to give it back. At no point was there a nonzero total angular momentum.
...BTW, you're still making the mistake of comparing two vectors of different units. Force and torque cannot compensate for each other....
Halc,there are two scenarios that need to be analyzed.1. With the CMGs NOT RUNNING/ACTUATED2. With the CMGs RUNNING/ACTUATED
1. The center of CD players (ISS) mass moves on a straight line and the CD players rotate when CD players are OFF (CDs inside do not rotate).2. The center of CD players (ISS) mass does not move on a straight line and the CD players do not rotate, they just wobble when CD players are ON (CDs inside rotate).Do you see the difference?This is what is at the core of the problem I am trying to point out,
Halc, is torque a force vector?
This is a little bit tricky question, because of the well balanced accelerating wheel. What is a torque for the accelerating wheel?
Is the wheel going to jump up due to the angular acceleration/deceleration, assuming angular acceleration is bigger than gravitational acceleration?