1. The problem statement, all variables and given/known data A railway carriage with a mass m = 2.05×104 kg is initially travelling to the left with a speed Vi = 3.24 m/s. It collides and couples with (get stuck to) two identical railway carriages move to the left with a speed of Ui = 2.36 m/s. What is the speed of the railway carriage after the collision? 2. Relevant equations P = m1v1 + m2v2 KE = 1/2mv2 KE (before collision) = 1/2m1v12 + 1/2m2v22 KE (after collision) = 1/2(m1+ m2)vf2 3. The attempt at a solution 1. P = (2.06×10^4 x 3.24) + 2(2.05×10^4 x 2.36) = 1.6x10^5 ∴ P = 1.6x10^5 = (m1 + 2m2)vf = 6.15x10^4 vf = (1.6x10^5) / (6.15x10^4) vf = 2.60 m/s But this answer is not correct... Can someone point out the parts I'm not doing correctly?