- #1

- 51

- 0

## Homework Statement

The neutral pion is an unstable particle that decays very quickly after its creation into two photons (“particles” of light: v = c, mo = 0). The pion has a rest-mass energy of 135 MeV. Consider a pion that has a kinetic energy of 90 MeV

1) Determine the v of this pion

2) Determine the momentum of the pion

3) Determine the sum of the energies of the photons

## Homework Equations

1) m

_{o}c

^{2}[tex]\gamma[/tex] = KE + Rest E

2) m

_{o}v[tex]\gamma[/tex] = p

3) E

_{photons}= pc

## The Attempt at a Solution

I'm pretty sure I got 1 and 2. For 1 I added the KE + RE, converted to proper units, and finally got v = .80c

For 2 I got p = 9.6 x 10

^{-20}kg m/s

Now I'm not so sure about #3. I think E

_{photons}= pc because momentum is conserved, and all of the pion's momentum gets turned into the photons' momentum. However, what about adding up the original rest mass energy + KE of the pion? If I do that I get a bigger energy then if I do pc. Thanks for all the help!