During a pool game the cue ball is shot at the red ball. When the cue ball strikes the red ball. The cue ball stops dead, and the red ball moves away at the same velocity the cue ball had before the collision. The type of collision represented in this example is: A. An elastic collision B. A perfectly inelastic collision C. An inelastic collision D. All of the above E. None of the above
Hint:A collision is described in physics as any occurrence in which two or more bodies exert forces on each other in a short period of time. Although the most general use of the word collision is an event in which two or more objects collide violently, the empirical meaning of the term has little to do with the severity of the force.
Complete answer: The collision is considered to be inelastic if any or all of the overall kinetic energy is lost (dissipated as heat, sound, etc. or consumed by the objects themselves); such collisions entail objects coming to a complete halt. A car accident is an example of such a wreck, when cars crumple internally rather than bouncing off of each other as they collide. This is by nature for the benefit of the passengers and spectators in the event of a collision; instead, the car's structure absorbs the impact force.
There is no kinetic energy loss in an elastic collision. If the balls have the same mass, their kinetic energies will be the same because their velocities are equal, because because only one ball is travelling before and after the collision, the overall kinetic energy will be stable, indicating that the collision is elastic. Total kinetic energy prior to collision = Total kinetic energy after collision
Hence, the correct answer is option A.
Note:The collision is considered to be completely elastic if all of the overall kinetic energy is conserved (i.e. no energy is emitted as sound, heat, or other forms of energy). Due to the second rule of thermodynamics, such a structure is an idealisation and cannot exist in fact.