Kinetic energy of a recoiling nucleus

1. Mar 1, 2009

roughtenator

A Fe nucleus at rest emits a 14.0-keV photon. Use conservation of energy and momentum to deduce the kinetic energy of the recoiling nucleus in electron volts. (Use Mc2 = 8.60E-9 J for the final state of the Fe nucleus.)

what I have so far is...

E = pc because E >> photon rest energy , which = 0 eV

P = E/C = 7.476 E-24

P1 = P2

I'm not sure what to do next.

Thanks in advance for the help!

2. Mar 1, 2009

malawi_glenn

what is the relation between Energy and kinetic energy in special relativity? And what is the relation between energy, momentum and mass in special relativity?

3. Mar 1, 2009

roughtenator

Relation between kinetic energy and total energy in special relativity is...
E = K + mc2
Relationship between mass, energy and momentum is...
E2 = P2C2 + (mc2)2

4. Mar 1, 2009

malawi_glenn

great, then can you find, from these two, a relation between momentum, mass and kinetic energy?

5. Mar 1, 2009

roughtenator

is this valid?

(K+MC2) = P2C2 + (MC2)2

then isolate K?

6. Mar 2, 2009

malawi_glenn

you forgot to square the left-hand side ...