Please help me! I have been thinking on this problem A car of mass 450kg travels east at 4.5m/s, and collides with a 550kg truck infront of it traveling east at 3.7m/s. What are their velocity after the elastic collision. I know the energy formula and the momentum formula, and I know that when the energy formular is divided by the momentum formula, it came out that: V1-V2=V'2-V'1 the ' sign means prime/final But I can't figure it out anyway... due to my stupidity... because V'2 and V'1 is unknown. Would anyone help me? If so, please explain to me how you would do it using the energy and momentum formula.