Glossary
Completely Inelastic Collision
A special type of inelastic collision where the colliding objects stick together after impact, moving as a single combined mass.
Example:
When a dart hits a target and embeds itself, the dart and target move together as one system, demonstrating a completely inelastic collision.
Conservation of Kinetic Energy
The principle that the total kinetic energy of a system remains constant before and after a collision, which only occurs in elastic collisions.
Example:
In an ideal scenario where two perfectly bouncy balls collide, their total conservation of kinetic energy would mean no energy is lost to sound or heat.
Conservation of Momentum
A fundamental principle stating that in an isolated system, the total momentum before a collision or interaction is equal to the total momentum after the collision or interaction.
Example:
When a cannon fires a projectile, the forward conservation of momentum of the projectile is balanced by the backward recoil of the cannon.
Elastic Collision
Collisions where both momentum and kinetic energy are conserved. Objects typically bounce off each other without permanent deformation or energy loss to other forms.
Example:
A perfectly executed shot in billiards, where the cue ball strikes another ball and both roll away cleanly, closely approximates an elastic collision.
Inelastic Collisions
Collisions where momentum is conserved, but kinetic energy is not, often due to its conversion into other forms like heat, sound, or deformation.
Example:
When a meteor strikes the Earth, much of its kinetic energy is converted into heat, sound, and deformation of the ground, making it an inelastic collision.
Kinetic Energy (KE)
The energy an object possesses due to its motion, calculated as half its mass times the square of its velocity ($KE = \frac{1}{2}mv^2$).
Example:
A fast-moving baseball has significant kinetic energy, which is why it can break a window upon impact.
Momentum
A vector quantity defined as the product of an object's mass and its velocity, representing its 'quantity of motion.'
Example:
A heavy train moving slowly has a large amount of momentum, making it difficult to stop.