The equation for perfectly inelastic collisions is m1(v1) + m2(v2) = (m1 + m2)vf. Object one has a mass of m1 and an initial velocity of v1. The mass of object two is m2, and the initial velocity of it is v2. The final velocity of both objects is vf.
Perfectly inelastic collisions result when two objects collide and stick together, moving in the same direction. A bug hitting the windshield of a car is an example of an inelastic collision. Before colliding, the bug and the car are moving separately, and after they are moving together. Kinetic energy is always lost in inelastic collisions because it is converted to other forms of energy.