Momentum
If an object is moving, it has momentum. This is what keeps an object moving in the same direction. The more momentum something has, the harder it is to change its direction or bring it to a stop.
So we can work out an object's momentum using the equation:
Momentum = mass × velocity
During an explosion or collision, the total momentum is conserved. This means the total momentum before the event is equal to the total momentum after the event. This is useful for studying collisions in space or stellar explosions.