V=? for Relativistic Mass,length contraction & time dilation

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SUMMARY

The discussion focuses on the velocity equations related to relativistic mass, length contraction, and time dilation. Key equations include the length contraction formula: v = c √{1-(l'/lo)^2} and the relationship l'/lo = √{1-v^2/c^2}. The concept of "relativistic mass" is deemed outdated and not widely used in modern physics, as it can lead to confusion in understanding relativity. Participants emphasize the importance of grasping the underlying principles of these equations rather than memorizing them for exams.

PREREQUISITES
  • Understanding of special relativity concepts
  • Familiarity with the speed of light (c) and its significance
  • Basic knowledge of algebra and solving equations
  • Awareness of historical context regarding relativistic mass
NEXT STEPS
  • Study the derivation of the time dilation formula in special relativity
  • Explore the implications of length contraction on moving objects
  • Research modern interpretations of mass in relativistic physics
  • Review educational resources on special relativity for clarity on outdated concepts
USEFUL FOR

Students of physics, educators teaching relativity, and anyone interested in deepening their understanding of special relativity concepts and equations.

Axidecimal
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Homework Statement


Velocity Equations for Relativistic Mass,length contraction and time dilation.
I was able to figure out one. This is not for homework. I want to learn these equations for future reference.

Homework Equations


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The Attempt at a Solution



Length Contraction : v = c √{1-(l'/lo)^2}
Time Dilation: ?
Mass: ?
 
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Just so I understand how you are thinking so I can answer properly:
How did you work out the length-contraction equation? Why not do the same thing for time dilation?

Note: no such thing as "relativistic mass". Used to be a thing but it turns out not to be much of a useful concept.
 
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l'/lo = √{1-v^2/c^2}
(l'/lo)^2 = 1-v^2/c^2
1-(l'/lo)^2 = v^2/c^2
√{1-(l'/lo)^2} = v/c
c√{1-(l'/lo)^2} = v

Mass increase has not been discontinued in my program.
 
Last edited:
Why not do the same thing for time dilation?

OK you need to do relativistic mass for passing exams - just understand that it is an out of date concept.
 
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1481091214815-575886308.jpg

I just copied the equations from wiki to this platform but i now have come to realize they are the same.
This is pretty self explanatory. i was given equations from my lessons that were essentially the same but all look different so i got confused. I didnt even look at the wiki equations closely until now :sorry:o_O:frown:
 
Last edited:
Simon Bridge said:
OK you need to do relativistic mass for passing exams - just understand that it is an out of date concept.
Better still: Point your teachers to my Insight post What is relativistic mass and why it is not used much? or refer them to me. It is simply a concept that is not used in physics today and it is really just confusing people to use it. Unfortunately, the concept permeates much of the introductory physics literature - which often is not written by people with specialist knowledge on relativity - and therefore becomes used by teachers at pre-university and introductory university level.
 
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Axidecimal said:
View attachment 110045
I just copied the equations from wiki to this platform but i now have come to realize they are the same.
This is pretty self explanatory. i was given equations from my lessons that were essentially the same but all look different so i got confused. I didnt even look at the wiki equations closely until now :sorry:o_O:frown:
Well done.
The form of the equations is ##x = \frac{y}{\sqrt{1-z^2}}## and you want to solve for ##z##.
It does not matter what the actual letters are.

It is more important to understand how to use the equations - that is the hard part to get your head around.
 

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