Key Concepts
* Momentum: A measure of an object's mass in motion. It's calculated as mass (m) multiplied by velocity (v): p = mv
* Conservation of Momentum: In a closed system (no external forces), the total momentum before a collision equals the total momentum after the collision.
How Momentum Changes
1. Perfectly Elastic Collision:
* Kinetic energy (energy of motion) is conserved.
* Objects bounce off each other with minimal energy loss.
* The total momentum of the system *remains the same*.
2. Inelastic Collision:
* Kinetic energy is *not* conserved. Some energy is converted to other forms like heat or sound.
* Objects can stick together or deform during the collision.
* The total momentum of the system *still remains the same*, but the momentum of each individual object changes.
Examples
* Car Collision: Two cars collide head-on. The total momentum of the system (both cars) before the collision equals the total momentum after the collision. However, individual car momentum changes drastically, often resulting in damage and possibly changes in direction.
* Billiard Balls: A cue ball strikes another ball. The cue ball slows down, while the other ball gains momentum and moves off. The total momentum of the system remains constant.
Important Notes
* External Forces: If external forces act on the system (like friction), momentum is not strictly conserved.
* Impulse: The change in momentum of an object is equal to the impulse applied to it. Impulse is calculated as force multiplied by the time over which the force acts.
In Summary
While the total momentum of a system remains constant in collisions, individual object momentum changes. The nature of the collision (elastic or inelastic) determines how the momentum is distributed among the objects involved.
