Density Formula for Moving Particles

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SUMMARY

The discussion centers on the concept of density for moving particles, highlighting the distinction between rest mass and relativistic mass as described by Einstein's General Theory of Relativity. It is established that while the formula for density is mass divided by volume, the perception of density changes based on the observer's frame of reference. For an external observer, the density of a moving particle appears to increase due to the relativistic effects of mass at high velocities. The conversation emphasizes the importance of context when applying the density formula to moving objects.

PREREQUISITES
  • Understanding of basic physics concepts, particularly mass and density
  • Familiarity with Einstein's General Theory of Relativity
  • Knowledge of relativistic mass and its implications
  • Concept of reference frames in physics
NEXT STEPS
  • Study the implications of relativistic mass on density calculations
  • Explore the differences between rest mass and relativistic mass in detail
  • Learn about reference frames and their impact on physical measurements
  • Investigate practical applications of density in relativistic contexts
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Students of physics, educators teaching relativity, and researchers exploring the implications of mass and density in high-velocity contexts.

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Hello;

I know that the formula for density is mass/volume. However, this is only true for rest mass. What about when the particle is moving?

Thanks.
 
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This opens up the whole can of worms about the different kinds of mass in relativity. I suppose the answer would depend on what you want to use the density of the moving object for.
 
Mass increases with velocity, right?

Do I have to use Einstein's General Theory of Relativity and somehow use that with my original density formula? I'm confused
 
Note that the particle itself would not know if it is moving or not, unless it was being accelerated. So according to the particle, it's density would not increase.
However, from the viewpoint of an external observer, it could be said that the density of the object had, in a way, increased.

In the end, whether this density is what would fit in with your usual concept of density or not, depends on what you want to use it for, as jtbell said.
 
However, from the viewpoint of an external observer, it could be said that the density of the object had, in a way, increased.

I don't get it... what do you mean by this?
 

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