How Fast is C Moving Relative to B?

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SUMMARY

In the discussion, the problem involves calculating the relative speed of object C moving towards A at 0.5c with respect to object B moving towards A at 0.4c. The solution utilizes the relativistic velocity addition formula: U = (U' + V) / (1 + VU'/c²). The calculated result indicates that C is moving towards B at a speed of c/8. The ambiguity regarding the direction of B and C relative to each other is acknowledged but does not affect the calculation of their relative speed towards A.

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  • Understanding of special relativity principles
  • Familiarity with the relativistic velocity addition formula
  • Knowledge of the speed of light as a constant (c)
  • Basic algebra for manipulating equations
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Homework Statement



relative to A, B is moving towards A at a speed of 0.4c. Farther out C is moving towards A at a speed of 0.5c. all motion is along the x-axis

how fast is C moving relative to B?



Homework Equations



U = (U' + V) / 1+ VU'/c^2



The Attempt at a Solution



0.4c- 0.5c / 1 - (0.4c * 0.5c) / c^2 = 0.125


C is moving at c/8 towards B

?
 
Physics news on Phys.org
As the problem is stated I'm not sure if B and C are heading in the same direction or heading towards each other. All we know for sure is that both B and C are moving towards A.
 

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