1. Elastic collisions: Objects bounce apart after they have collided with each
other; Kinetic Energy is CONSERVED so you can use Conservation of
Mechanical Energy; Momentum is CONSERVED so you can use
Conservation of Linear Momentum.
Inelastic collision: Objects stick together/embedded after collision; Kinetic
Energy NOT conserved so CANNOT use Conservation of Mechanical
Energy; But Momentum is CONSERVED so you can use C.O.L.M