Vocabulary:

Pressure: (the symbol: P) is the force per unit area applied in a direction perpendicular to the surface of an object.

PSI: Pound per square inch.

Center of Mass: The terms "center of mass" and "center of gravity" are used synonymously in a uniform gravity field to represent the unique point in an object or system which can be used to describe the system's response to external forces.

Propulsion: The action of driving or pushing forward.

Newton's Laws:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. 

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.  

III. For every action there is an equal and opposite reaction.