A collision in which some kinetic energy is lost is a (n) collision. A collision in which the objects become one and move together is a (n) inelastic collision.

A collision in which some kinetic energy is lost is a inelastic collision. A collision in which the objects become one and move together is a perfectly inelastic collision.

Inelastic collision. An inelastic collision is any collision where some kinetic energy is lost and converted to another form. In a case where two objects collide and move together, energy is lost at the collision. An elastic collision would be one where no energy is lost.