By Smithsonian's National Air and Space Museum
Momentum describes the quantity of motion that an object has.
The amount of momentum that an object has is dependent upon how much mass is moving and how fast the stuff is moving.
It is a vector quantity because it has both a magnitude (size or speed) and an associated direction. Vectors are used in physics to help describe motion.
For example, a car has no momentum when it is standing still. When it begins to move, it will have momentum in the same direction as it is travelling. The faster the car drives, the larger its momentum will be.
Momentum can be calculated using the equation momentum = mass × velocity or p=mv where momentum (p) is measured in kilogram meters per second (kg m/s), mass (m) is measured in kilograms (kg) and velocity (v) is measured in metres per second (m/s).
artsandculture.google.com