Torque & Rotation: 2 Axes, Tilting Possible?

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52 replies · 6K views
Sundown444 said:
So, they can rotate around any axis/number of axes, then?
No. The notion of "rotation" does not apply.
 
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jbriggs444 said:
No. The notion of "rotation" does not apply.

So they are not really rotating, something like that?
 
Sundown444 said:
So they are not really rotating, something like that?
The motion of a non-rigid object cannot always be described as a rotation. Sometimes it's just "squishing" or "swirling".
 
jbriggs444 said:
The motion of a non-rigid object cannot always be described as a rotation. Sometimes it's just "squishing" or "swirling".

And how would you define "squishing"? Is that what they are doing in the video?
 
russ_watters said:
I really think this is going down an unnecessary road. @Sundown444 you seem to be deviating from the answer you got and seemed to understand in post #2. Why?

*sigh* Wasn't aware of that. I thought the video I posted was related to my original question, due to how some of the divers rotated. In fact, those divers rotation was mainly what I was asking about to begin with. I just didn't see the need to post that video for some reason until now.
 
Sundown444 said:
*sigh* Wasn't aware of that. I thought the video I posted was related to my original question, due to how some of the divers rotated. In fact, those divers rotation was mainly what I was asking about to begin with. I just didn't see the need to post that video for some reason until now.
You didn't ask a specific question (just "how do you explain...") in your recent reboot, but yes, I too thought it was related to your first post. So why isn't the answer, "yes" (with added depth), good enough anymore? What happened? It feels like we are starting over from scratch, but all the previous posts are still there!

Is there something you believe, but don't want to admit? Something you want to know, but don't want to ask?
 
russ_watters said:
You didn't ask a specific question (just "how do you explain...") in your recent reboot, but yes, I too thought it was related to your first post. So why isn't the answer, "yes" (with added depth), good enough anymore? What happened? It feels like we are starting over from scratch, but all the previous posts are still there!

Is there something you believe, but don't want to admit? Something you want to know, but don't want to ask?

No, I knew of the answers before this thread. I just wanted to make sure with this video. Double checking, that is all. That said, is it still the same answer as before?
 
Sundown444 said:
No, I knew of the answers before this thread. I just wanted to make sure with this video. Double checking, that is all. That said, is it still the same answer as before?
Yes, the answer is still yes.
 
russ_watters said:
Yes, the answer is still yes.

Looks like there is all I need to know, then. Still a bit confused about the divers, though. Would looking back on previous posts on this topic help me out?
 
Sundown444 said:
Looks like there is all I need to know, then. Still a bit confused about the divers, though. Would looking back on previous posts on this topic help me out?
Probably. Also, using declarative statements and direct questions would help us target our answers better. For example, when you say, "How do you explain...?" after having already received an explanation, it implies you think something is wrong with the explanation, without actually telling us what.
 
russ_watters said:
Probably. Also, using declarative statements and direct questions would help us target our answers better. For example, when you say, "How do you explain...?" after having already received an explanation, it implies you think something is wrong with the explanation, without actually telling us what.

Alright, I will keep that in mind. Thanks. I might have some other questions later, but they will be about the previous explanations in which some parts of them I might not right away understand, if that is okay.
 
Sundown444 said:
What I meant, is that the divers seem to be doing somersaults and twists at the same time. If I have this down right, I wonder how it is possible?
Training.
 
How about...

A divers body can be modeled as a set of cylinders connected together by joints that have various degrees of flexibility. This allows some body parts and groups of body parts to rotate about different axis with respect to each other. Said axis are frequently changing.

...well its the best summary I can manage.
 
CWatters said:
A divers body can be modeled as a set of cylinders connected together by joints that have various degrees of flexibility. This allows some body parts and groups of body parts to rotate about different axis with respect to each other. Said axis are frequently changing.
Yes, you have relative rotations of segments. But I wouldn't say that "body rotates around multiple axes", because the body as a whole doesn't have a defined angular velocity here. However, it does have a total angular momentum vector, which is constant during the fall (ignoring aerodynamics).
 
Agreed. I tried to choose the words carefully.
 
CWatters said:
How about...

A divers body can be modeled as a set of cylinders connected together by joints that have various degrees of flexibility. This allows some body parts and groups of body parts to rotate about different axis with respect to each other. Said axis are frequently changing.

...well its the best summary I can manage.

So, what are you saying? The body can appear to rotate around more than one axis with use of relative body parts, or even by rearranging body parts, maybe?
 
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Sundown444 said:
The body can change rotational axis
If the body does not even have a rotational axis, the notion of changing its rotational axis does not arise.
 
jbriggs444 said:
If the body does not even have a rotational axis, the notion of changing its rotational axis does not arise.

Oops! My bad! Forgot about that for a second.
 
Sundown444 said:
The body can appear...
Who knows how it appears to you. It's like explaining how colors appear.

Sundown444 said:
...rotate around more than one axis ...
Not a good description of what actually happens, as explained in post #45 on others.
 
A.T. said:
Who knows how it appears to you. It's like explaining how colors appear.Not a good description of what actually happens, as explained in post #45 on others.

Then what about the rearranging body parts part? Does rearranging body parts have to do with any of this?
 
Sundown444 said:
...rearranging body parts ...
Sounds like a serial killer making space in the fridge. What's wrong with saying "relative motion of body segments"?
 
A.T. said:
Sounds like a serial killer making space in the fridge. What's wrong with saying "relative motion of body segments"?

Ugh, no, I meant rearranging one's own body parts as in moving them around as they are diving. Relative motion of body segments is good too, but there is no need to make what I said seem what it is not.

I know this is probably science talk, but still...
 
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