Elastic Collisions: Kinetic energy is conserved, objects bounce off. | Inelastic Collisions: Kinetic energy is not conserved, energy lost as heat/sound, objects may stick.

Closed System: No exchange of matter/energy, momentum conserved. | Open System: Exchange of matter/energy, momentum may not be conserved.

Momentum is a measure of how much "oomph" an object has when it's moving; it's essentially its resistance to changes in motion.

$p = mv$, where $p$ = momentum (kg⋅m/s), $m$ = mass (kg), and $v$ = velocity (m/s).

Impulse is the change in an object's momentum caused by a force acting over a period of time.

$J = \Delta p = F\Delta t$, where $J$ = impulse (N⋅s or kg⋅m/s), $\Delta p$ = change in momentum, $F$ = force (N), and $\Delta t$ = time interval (s).

A system where no matter or energy is exchanged with the surroundings; total momentum remains constant.

A system where matter or energy can be exchanged with the surroundings; total momentum may not be constant.

In a closed system, the total momentum remains constant. The total momentum before an event equals the total momentum after the event.

A collision in which kinetic energy is conserved. Objects bounce off each other.

A collision in which kinetic energy is not conserved. Some energy is lost as heat or sound. Objects may stick together.

Momentum is a measure of how much 'oomph' an object has when it's moving; its resistance to changes in motion.

$p = mv$, where $p$ = momentum, $m$ = mass, and $v$ = velocity.

Impulse is the change in an object's momentum caused by a force acting over a period of time.

$J = \Delta p = F\Delta t$, where $J$ = impulse, $\Delta p$ = change in momentum, $F$ = force, and $\Delta t$ = time interval.

A closed system is one where no matter or energy is exchanged with the surroundings; total momentum remains constant.

An open system is one where matter or energy can be exchanged with the surroundings; total momentum may not be constant.