Lorentz Contraction: Gaining Mass & Shrinking

Swankie
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Hi all, modern physics student here. If the Lorentz contraction occurs at relativistic speeds, how does it gain mass yet get shorter?

The best I can think of is that it has to depend in which reference frame one is in at the time. Does anyone know any useful links where I can read about this?
 
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You're right about the dependence on a reference frame. This forum is a good place to find information on this subject. Do a search for "mass" in the title and pick the threads that address your question. Click on this link to see the result of this search:

https://www.physicsforums.com/search.php?searchid=3078794
 
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Swankie said:
If the Lorentz contraction occurs at relativistic speeds,

Length contraction occurs at ALL non-zero speeds.

Swankie said:
how does it gain mass

An object does NOT gain mass due to velocity. It gains "relativistic mass," but relativistic mass is a virtually useless quantity which physicists (for that reason) don't use anymore.

Swankie said:
yet get shorter?

Why does this seem paradoxical to you? Why do you think that the measured length of an object would have any effect on its mass?

Swankie said:
The best I can think of is that it has to depend in which reference frame one is in at the time.

Well yes, length and relativistic mass are certainly frame-dependent quantities. You could, for example, measure an object from a reference frame in which it is at rest. You could also measure the same object from a reference frame in which it has a velocity of 99.999% the speed of light. Obviously the two measurements will differ.
 
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