I Clockwise spinning gyroscope

A

Abokoj

So I've just started reading into how gyroscopes work and I've hit a wall. Previously I thought that the upwards angular momentum kept the spinning object up straight, but why does it do the same if it's spinning clockwise too even though the angular momentum would be pointing down? Does the angular momentum vector not have anything to do with it in the first place?
Even when you spin it clockwise and the precession becomes also clockwise the gyroscope will eventually straighteb up even when the angular momentum is pointing down for the precession too.
It feels like my understanding of the topic is not accurate. I'd appreciate some clarification, thanks.
 

scottdave

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Gyroscopic precession can get confusing. Try watching this video, to see if it helps. Derek often explains things in ways that allow me go go "Ahah!"

 
A

Abokoj

Gyroscopic precession can get confusing. Try watching this video, to see if it helps. Derek often explains things in ways that allow me go go "Ahah!"

Yeah Derek is great. I've seen the video too but it I'm looking for a clockwise movment where the angular momentum is pointing "inwards" not "outwards" if you understand what i mean
 

scottdave

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Yeah Derek is great. I've seen the video too but it I'm looking for a clockwise movment where the angular momentum is pointing "inwards" not "outwards" if you understand what i mean
I am trying to imagine what you mean. Is there a way that you can sketch something and link to a picture?
 

scottdave

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OK, so I think you are saying like if you have a top spinning, so that it's axis is vertical (angular momentum vector pointing up, or pointing down depending on rotation)?
Edit:
So if the top starts to "fall down" this creates a torque, which has a horizontal pointing vector. The net effect will be another vector, perpendicular to both of those.
 
The video just adds confusion... no questions are answered.

Does the torque vector represent a force, or some kind of pseudo-force, or is it an arbitrary convention that is not a real vector, showing only magnitude but not direction, using the two directions as proxies for the direction of rotation?

The video seems to treat torque vectors as forces with direction and magnitude, but if the red torque arrow is pointing through the axis parallel to the ground, and if it is a vector for force, why does the wheel not move in that direction?

When the red and blue arrows are combined, why do they not form a vector sum that is in the plane parallel to the ground, and the wheel move in that direction rather than processing?

He shows the blue vector tailed at the rope end and he points toward the camera to indicate its direction, but when he is combining the red and blue arrows he holds his hand at the end of the axle opposite the rope connection to indicate the tailed end of the blue vector - he is showing the blue force moved over to the other end of the axle where its lateral component is now on the arrowhead side of red arrow... which he uses to explain the rotation direction of procession. But if he left the blue arrow tailed at the rope end of the axle where it actually is, then the net result looks like the direction of procession should be the other way.

red arrow points left, tailed at the center of axle
blue arrow point toward camera, tailed to rope end of axle

viewed from above...
red arrow blue arrow
< center of axle V

viewed from above the rotation should be clockwise, but the video shows anticlockwise
 

scottdave

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I have seen a better video, but cannot recall who made it. Sorry. The torque vector is not a force pointing in that direction, but mathematical operations can act with this vector.
 
A

Abokoj

OK, so I think you are saying like if you have a top spinning, so that it's axis is vertical (angular momentum vector pointing up, or pointing down depending on rotation)?
Edit:
So if the top starts to "fall down" this creates a torque, which has a horizontal pointing vector. The net effect will be another vector, perpendicular to both of those.
OK, so I think you are saying like if you have a top spinning, so that it's axis is vertical (angular momentum vector pointing up, or pointing down depending on rotation)?
Edit:
So if the top starts to "fall down" this creates a torque, which has a horizontal pointing vector. The net effect will be another vector, perpendicular to both of those.
I have seen a better video, but cannot recall who made it. Sorry. The torque vector is not a force pointing in that direction, but mathematical operations can act with this vector.
I was thinking something like this when the wheel is spinning clockwise and angular momentum is "inwards". Is this way of thinking wrong and how so?
 

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So I've just started reading into how gyroscopes work and I've hit a wall. Previously I thought that the upwards angular momentum kept the spinning object up straight, but why does it do the same if it's spinning clockwise too even though the angular momentum would be pointing down? Does the angular momentum vector not have anything to do with it in the first place?
Even when you spin it clockwise and the precession becomes also clockwise the gyroscope will eventually straighteb up even when the angular momentum is pointing down for the precession too.
It feels like my understanding of the topic is not accurate. I'd appreciate some clarification, thanks.
"Upwards angular momentum kept the spinning object up straight"

No. Absolute not. That is just completely wrong. I am Just trying to be clear here. :smile:

Ok now my main point:

There are two motions occurring: the precession motion and the spinning motion. If we look at the spinning disk, we can point at its lower side and its upper side. The two motions are interfering constructively at the lower side, and destructively at the upper side.

If both of the two motions were reversed, the sides would stay the same, and the gyro's ability to stay upright would stay the same.

When I say "the two motions are interfering constructively at the lower side" I mean the atoms of the disk have the highest speed at the lower side of the disk.
 
Last edited:
A

Abokoj

"Upwards angular momentum kept the spinning object up straight"

No. Absolute not. That is just completely wrong. I am Just trying to be clear here. :smile:

Ok now my main point:

There are two motions occurring: the precession motion and the spinning motion. If we look at the spinning disk, we can point at its lower side and its upper side. The two motions are interfering constructively at the lower side, and destructively at the upper side.

If both of the two motions were reversed, the sides would stay the same, and the gyro's ability to stay upright would stay the same.

When I say "the two motions are interfering constructively at the lower side" I mean the atoms of the disk have the highest speed at the lower side of the disk.
Thanks for the help. So how does it work when the spinning top is spinning while standing ip straight. There wouldn't be any lower or upper side, are you saying that angular momentum does keep it up but not in a vector kind of way?
 

scottdave

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I think that was the one @A.T. It shows what is happening, starting with the simple example of a single satellite. The vectors help you do the math, but it really helps to intuitively understand what is happening.
 
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Thanks for the help. So how does it work when the spinning top is spinning while standing ip straight. There wouldn't be any lower or upper side, are you saying that angular momentum does keep it up but not in a vector kind of way?
In that case there just is no torque trying to make the top fall, and no torque trying to keep the top up straight, so the top stays up straight. I mean if the top really is in perfect balance, not leaning at all.

I recommend thinking about a top that leans a lot and precesses in a large circle. I recommend thinking the circling motion causing a centrifugal force on the disk, and the spinning of the disk increasing the centrifugal force on one side of the disk, and reducing the centrifugal force on the other side.
 

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