1. The problem statement, all variables and given/known data 12-16 K + mesons can be photoproduced by the reaction γ + p → K+ + Λ where the initial proton is at rest in the lab. From the conservation laws, discover if it is possible for either the K+ or the Λ to be at rest in the lab, and for what photon energy (in terms of the particle masses) this could happen. 2. Relevant equations E^2 = p^2c^2 + m^2c^4 p = mv E = mc^2 3. The attempt at a solution I'm really stuck on this problem. It's probably more of an algebraic answer, because I believe I'm supposed to somehow get the two equations of energy and momentum conservation to have like terms and then combine them somehow, but I'm at a loss as to what to do. Any help is appreciated.