How would a long object move?

  • Thread starter Edward Solomo
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In summary, the conversation discusses the concept of a long, inflexible rod and how it would move if a force was applied to one end. The participants contemplate the effects of molecular composition and the speed of sound in relation to this scenario. It is also mentioned that the speed of light in vacuum serves as a theoretical limit for the speed of sound.
  • #1
Edward Solomo
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How would a "long" object move?

My question is seemingly simple.

Let us suppose that we had an unbreakable/inflexible rod whose length was 11.8 million miles in length (one light-minute). Now assume that we applied enough force at one end of the rod to move the entire rod altogether. As nothing can travel faster than the speed of light, how long would it take for the opposite end of the rod to move? Does the motion of the rod become a wave?
 
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  • #2


An inflexible rod wouldn't move because it doesn't exist. But yes, a real rod begins to move by pasing the force through the rod in the form of a longitudinal wave: a sound wave.
 
  • #3


Sure. Let's say this rode is made from a chunk of a neutron star. Well, if this is the case, it will still take more than a second (several hours i guess) before the other end moves. But for a hypothetical stiff, rigid rode I think it can never be at rest neither can it be accelerated. This means at any given time both ends are moving at the same speed irrespective of any gravitavion fields. Think ether. NOTE: This is my own speculation. It should not be taken as fact. Thanks.
 
  • #4


russ_watters said:
An inflexible rod wouldn't move because it doesn't exist. But yes, a real rod begins to move by passing the force through the rod in the form of a longitudinal wave: a sound wave.

This suggests that the molecular composition would affect the "speed of motion" of a rod.

After doing a little reading (now since I know what to read), I saw some sources calling it "mechanical information" that travels in sound waves, as the guy said above. Is there any theoretical limit on the speed of sound?
 
  • #5


Edward Solomo said:
This suggests that the molecular composition would affect the "speed of motion" of a rod.
Yes, a rubber rod beheves differently than a steel rod, when rotated.

Edward Solomo said:
After doing a little reading (now since I know what to read), I saw some sources calling it "mechanical information" that travels in sound waves, as the guy said above. Is there any theoretical limit on the speed of sound?
Yes, the speed of light in vacuum. The electromagnetic interactions between the atoms of the rod, cannot go faster than that.
 

1. How does the length of an object affect its movement?

The length of an object does not directly affect its movement. Rather, the shape and weight distribution of the object play a larger role in determining how it moves.

2. How would a long object move differently than a short object?

A long object may have a higher moment of inertia and be more prone to rotational motion, while a short object may be more stable and experience less rotational movement.

3. Does the material of the object impact its movement?

Yes, the material of an object can impact its movement. For example, a long, thin object made of a light material may be more susceptible to being affected by wind or air resistance, while a shorter, heavier object may be less affected by these forces.

4. How does the surface on which the object is moving affect its movement?

The surface on which an object is moving can greatly impact its movement. For example, a long object may have more friction and resistance when moving on a rough surface compared to a smooth surface.

5. Can the movement of a long object be accurately predicted?

The movement of any object can be accurately predicted using mathematical equations and principles of physics, however, external factors such as air resistance, surface conditions, and other variables may affect the actual movement of a long object in real-world scenarios.

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