- #1
Brewer
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Homework Statement
A K-meson at rest decays into two pi-mesons, and each pi meson has a speed of 0.85c.
If a K-meson traveling at a speed of 0.9c decays, what is the greatest speed the one of the pi-mesons can have?
Homework Equations
[tex]u\prime = \frac{u-v}{1-\frac{v}{c^2}u}[/tex]
The Attempt at a Solution
After plugging in v=0.9c and u=0.85c I get 3 different answers (3 different derivations of the above equation)
Initially I got 1.11c which is clearly wrong, I think that answer came from just not cancelling properly and putting things in my calculator wrong.
Next I got a value of -0.213c from the above equation that I just copied from my notes.
Finally I got a value -0.213c from a similar equation to that above, but with all the signs on the RHS switched, when I tried to derive the equation. (I didn't actually know that this was the same answer - I've only just worked out the fractional value while typing this!). I am however confused, as surely a complete change of sign throughout the equation would change the sign of the answer. So why have I got the same answer?
Any help at all would be gratefully received - my main problem with Special Relativity is deciding which equation to use for the data given.