How Does Object Collision Work in Space?

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Discussion Overview

The discussion explores the dynamics of object collisions in space, specifically focusing on how a large cube would behave when struck by a smaller, high-velocity object. Participants consider the implications of the cube's rotation, inertia, and the nature of motion in a microgravity environment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a cube traveling in space would not spin uniformly when struck on its edge, implying that it would wobble due to the lack of a tethered central axis.
  • Another participant introduces the concept of inertia tensors, noting that a cube has a scalar inertia tensor, which may lead to less complex behavior compared to other shapes like a book, which has three different principal moments of inertia.
  • A different viewpoint emphasizes that if the cube is hit precisely, it could spin without wobbling, although it would still drift slightly.
  • One participant mentions that interesting motion occurs only when the principal moments of inertia differ, indicating that the cube's symmetrical shape limits its dynamic behavior.
  • The wobbling motion is attributed to the torque-free equations of motion for rigid bodies, specifically referencing the (\mathbf I \vec{\omega})\times \vec{\omega} term.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of the cube upon collision, with some agreeing on the wobbling effect while others debate the conditions under which uniform spinning might occur. No consensus is reached on the overall dynamics of the situation.

Contextual Notes

Participants note the complexity of motion in space and the influence of inertia on the behavior of objects, but do not resolve the implications of different shapes or the precise conditions required for uniform motion.

OneCookie
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Should an object for argument sake a cube be traveling in space at a stable rotation, if a small object traveling at a high velocity collided with the edge of the cube enough so that on Earth if fastened the cube would spin. in space however would this object spin/rotate in a single position or move awkwardly in a almost random direction. If so would the actions of the collision work when the small object colliding with the cube remains the same size yet the cube is 100x its size.

Random debate between friends, however neither of us have the knowledge required to actively agree with certainty on any particular point. if it requires any more explanation please let me know.
 
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The object is a cube, so it presumably has a scalar inertia tensor. The behavior for such an object is rather uninteresting. If on the other hand the spaceship was a book (three different principal moments of inertia) the behavior is quite complex. Now you can get into a situation where angular velocity and angular momentum point in different directions. The object will exhibit all kinds of weird behavior. Angular momentum will still be constant, but angular velocity is not. As Goldstein put it, "The polhode rolls without slipping on the herpolhode lying in the invariable plane."
 
The object (large cube) in space if hit on its edge would not spin in any sort of uniform fashion.
Because its central axis is not tethered to any stationary object.
In 99.999% of instances the large cube would wobble about all over the place. But if you could hit the cube very very precisely you could get it to spin without wobbling, BUT it would drift ever so slightly.
 
solar71 said:
The object (large cube) in space if hit on its edge would not spin in any sort of uniform fashion.
A cube will do just that. You need at least one of the principle moments of inertia to differ from the other two to get any kind of interesting motion. But even then it won't be that interesting. Things only get really interesting when all three principal moments of inertia are different from one another.

The wobbling results from the [itex](\mathbf I \vec{\omega})\times \vec{\omega}[/itex] term in the torque-free equations of motion for a rigid body.
 

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