Hi I have a simple question about inelastic collisions. Clearly energy cannot be conserved because when two things hit, they will create friction, noise, heat and other forms of nonconservative forces, but my question involves momentum. When we solve a problem we conserve momentum, in any collision. Is the reason why we can do this becuase we only conserve it for the instant that they come into contact. because in the case of a balistic pendululm, the thing eventually stops, so obviously momentum cannot be conserved throughout the entire trial of the experiment, at once point the pendulum reaches its max height and stops, so the momentum would be zero. The thing that gives me a little trouble is that energy is conserved immeditaly after the collision, so therefore, mechanical energy cannot be lost during this phase. That only leaves the instant when the two objects collide for energy to be lost. Well if this is the only point in which energy can be lost, how come it would not effect the momentum. It is usually, [tex] m_1v_1 = (m_1 + M_2) v_f [/tex] . But how come the final momentum is not lost due to the energy losses at that point. Ive kind of been doing circles around this in my reasoning for the last two days. arg.