Elastic scattering energy transfer without initial energy given

[matt222]

Homework Statement

Homework Equations

T=2*(m*M/(m+M)^2)*E(initial)*(1-cos(angle)), T is transferred energy from the neutron to the target.

displacement energy for Zr=40eV

The Attempt at a Solution

the question is strange for me it seems to me there is a trick since we don't have the initial energy of the incident particle!

I can't start solving without knowing the energy of the incident particle! any help please!

 

[HallsofIvy]

What are you trying to solve that equation for? You are given everything except the initial energy. Solve for that and use it to find the initial speed of the neutron.

 

[matt222]

Yes this is the trick now!
we need to find the minimum energy (in eV) of the neutron to displace two Zr in a row
what i can do is as follow:

total incident neutron energy is equal E, transferred energy to the target is T, neutron energy after scattering is Q, so that totat energy is :

E=T+Q

BUT here i lost what do you think about my idea