The Attempt at a Solution
I tried doing MV=m1v1f+m2v2f
I know that the sum of the momentum of the two parts is equal to the the momentum of the the full shell. Since I have two unknowns, I used the conservation of energy. I set used KE=KE1+KE2. The kinetic of the full shell equals to the sum of the kinetic energy of the two parts. Since I have two unknowns here too, I used a system of equations solve for v. Am I on the right path? I found two "ms" didn't add up to 5kg. Thank you in advance.