Glossary
Closed System
A system where no external forces act upon it, allowing for the conservation of total linear momentum.
Example:
Two ice skaters pushing off each other on a frictionless rink can be considered a closed system for analyzing their momentum.
Collision
An event where two or more objects exert forces on each other for a short period, resulting in a change in their motion.
Example:
The moment a cue ball strikes another billiard ball is a classic example of a collision.
Conservation of Linear Momentum
A fundamental principle stating that in a closed system, the total linear momentum remains constant, meaning the initial total momentum equals the final total momentum.
Example:
When a rocket expels exhaust gases, the total conservation of linear momentum ensures that the rocket gains forward momentum equal and opposite to the momentum of the expelled gases.
Elastic Collisions
A type of collision where both linear momentum and kinetic energy are conserved, typically characterized by objects bouncing off each other without deformation.
Example:
The ideal bouncing of a superball off a hard floor closely approximates an elastic collision, as very little energy is lost.
Impulse
The change in an object's momentum, calculated as the product of the net force acting on the object and the time interval over which the force acts.
Example:
A baseball bat hitting a ball delivers a large impulse over a short time, causing a significant change in the ball's momentum.
Inelastic Collisions
A type of collision where linear momentum is conserved, but kinetic energy is not conserved, often due to energy conversion into heat, sound, or deformation.
Example:
When a car crashes into a wall and crumples, it's an inelastic collision because kinetic energy is lost to deforming the vehicle.
Momentum
A vector quantity that measures an object's motion, defined as the product of its mass and velocity.
Example:
A bowling ball rolling down the lane has significant momentum due to its large mass and speed.
Newton's Third Law
States that for every action, there is an equal and opposite reaction, which is the underlying reason why momentum is conserved in interactions.
Example:
When you jump, your feet exert a downward force on the Earth, and by Newton's Third Law, the Earth exerts an equal and opposite upward force on you, propelling you into the air.
Perfectly Inelastic Collisions
A specific type of inelastic collision where the colliding objects stick together after impact, resulting in the maximum possible loss of kinetic energy.
Example:
If a dart hits a target and embeds itself, it's a perfectly inelastic collision because the dart and target move as one combined mass afterward.