Object a has mass ma = 10 kg and initial momentum a, i = < 15, -8, 0 > kg · m/s, just before it strikes object b, which has mass mb = 12 kg. just before the collision object b has initial momentum b, i = < 3, 5, 0 > kg · m/s.

When the displacement of a mass on a spring is 12a the half of the amplitude, what fraction of the mechanical energy is kinetic energy? at what displacement, as a fraction of a, is the mechanical energy half kinetic and half potential?