The velocity of the system's center of mass.

$$v_{cm} = \frac{\sum \vec{p}}{\sum m}$$ where $\sum \vec{p}$ is the sum of all individual object momenta and $\sum m$ is the total mass of the system.

Sum of all individual momenta in a system.

Impulse ($j$) is the change in momentum ($\Delta p$) of a system: $$j = \Delta p$$

Any change in momentum for one object is balanced by an equal and opposite change in momentum for another object (Newton's Third Law).

Impulse is equal to the change in momentum: $$j = \Delta p$$

A measure of an object's mass in motion, quantifying how much 'oomph' it has.

The average velocity of a system of objects, treating the system as a single entity.

The change in momentum of an object when the object is acted upon by a force for an interval of time. Mathematically, it's the integral of force with respect to time, but more simply, it is the product of the average force and the time interval for which it acts.

A system where no net external force acts, and thus the total momentum remains constant.

The change in a system's total momentum equals the impulse exerted on it from outside the system: $\vec{J}=\Delta \vec{p}$

Add up all the individual momenta, remembering that momentum is a vector (direction matters!).

Define your system to identify if external forces are present and if momentum is conserved.