In completely inelastic collision, m1v1+m2v2=m1v+m2v after collision both particle have common velocity v, so all energy is not lost ∴ Statement −1 is true The principle of conservation of momentum applicable for all kinds of collisions. So statement −2 is also true. Statement - 2 explains statement - 1 correctly because applying the principle of conservation of momentum, we can get the common velocity and hence the kinetic energy of the combined body.