Final answer:
The best definition of a collision is a car colliding with an object or the upset of a car. Collisions can be elastic, where kinetic energy is conserved, or inelastic, where kinetic energy is lost and objects may stick together. The conservation of momentum is a key principle in any collision.
Step-by-step explanation:
In physics, the term collision refers to an event where two or more objects exert force on each other for a relatively short time. Among the given options, the best definition of a collision in a physical context would be option c: a car collides with an object or the upset of a car.
However, the technical definitions involve details about the nature of the collision. An elastic collision is characterized by the conservation of kinetic energy before and after the collision. Examples include a football player colliding with another or a racket hitting a ball, provided they do not stick together and internal kinetic energy is not lost. In contrast, an inelastic collision occurs when the colliding objects stick together after impact, resulting in the loss of some kinetic energy. For instance, a bullet fired into a wooden block that becomes embedded and acts as a ballistic pendulum illustrates an inelastic collision.
Understanding collisions is crucial, especially when considering momentum conservation. In any type of collision—whether elastic or inelastic—the total momentum of the system is conserved, assuming no external forces act upon it. This is evident in traffic collisions, where momentum is transferred from one vehicle to another.