Re: Rotation of a body in free space.

On Jul 31, 6:05 pm, "hhc...@xxxxxxxxx" <hhc...@xxxxxxxxx> wrote:
On Jul 31, 5:28 pm, rsprawls <rspra...@xxxxxxxxx> wrote:

It's been a while since my last physics class. I have been doing some
research into rotation and torque, but it all assumes the axis of
rotation is fixed, that is it rotates freely, but it doesn't move
linearly in 3D space. I want to model the proper Newtonian movement
of a object that has a moment of inertia, but is not fixed in space.

As an example of what I'm trying to illustrate: An astronaut in orbit
taps one end of a free floating wrench. It's going to spin, sure.
But it won't spin in place. It'll spin away. What subjects do I need
to research to find at least a Newtonian level of modeling?

By Newtonian, I mean not requiring tensors. Vectors are fine (even
though I know vectors hadn't been invented when Newton was breathing).
I learned about and remember vectors. I never learned about tensors.

Likely your best bet to understand the motion of an unconstrained 3-
dimensional body in free space is to borrow or purchase a really goog
textbook on classical mechanics or theoretical mechanics. Look for a
chapter on "Motion of a rigid body in three dimensions" or similar
chapter title. Likely it will be one of the last chapters in the
textbook, for reasons that will become obvious when you study it.

I'm looking for one now. I may return to studies, for refresher and
for the joy and sake of learning. It's goal orientated right now.
I'm modeling motion in the vacumn of space, but it needs to remain
computationally doable in real-time, so I'm not looking to model
gravity wells (at this time unless it can all be pre-computed).

I am designing coarse 3D models that I plan on putting through another
program to find the moment of initertia with respect to all three axis
within a certain degree of error. I plan to do this by assuming an
average density of material, distributed evenly throughout it's body,
to make it simpler. I'll take into account larger volumetric sections
of the model, but I don't want to try figuring in fluid mecahnics and
how open space within the model affects it's motion...however... maybe
for the future.

Thanks all for your help.

.

Relevant Pages

  • Re: Puzzling Questions
    ... Wouldn't it have to be internal, rather than external, for rotation to ... Some argue that with respect to the Earth, the Moon does not spin because we see ... rotational motion can be demonstrated in different reference frames. ... Getting back to your original question about rotation in the universe - we can ...
    (sci.astro)
  • Re: Johnny Carson
    ... and the relationship of the Earth's rotational axis to this motion. ... and on the orientation of its axis of rotation over ... this role as a mediating factor is somewhat greater than what ...
    (sci.astro.amateur)
  • Re: Dance definitions: spin, turn, twirl, [other related]?
    ... This axis runs roughly from the ... a "spin" is only possible if the axis is vertical ... If the axis of "rotation" is not perpendicular, ... non-rotating leg being extended out. ...
    (rec.arts.dance)
  • Re: rotating magnetic field
    ... no density change takes place in rotation. ... when the orientation of that relative motion is not resulting in a change ... of the magnitude and direction of the magnet. ... I speculate that perhaps the spin alignment of the atoms of the magnet is ...
    (sci.physics.electromag)
  • Re: Spinning cube question
    ... |> "Is it possible to a spin a cube so that at each corner of the ... How about if the rotation is occuring along all 3 planes? ... east to west spin, ... rotations all occuring on a different axis that meet ...
    (sci.physics)