Principles of Jet Propulsion:

Newton's Laws of Motion. To understand the basic principles of jet propulsion it is necessary to understand the practical application of Sir Isaac Newton's Laws of Motion.  There are three laws.

1. The First Law States.  A mass will remain stationary until acted upon by a force. If the mass is already moving at a constant speed in a straight line, it will. continue to move at that constant speed in a straight line until acted upon by a force.

2. The Second Law States.  When a force acts on a mass the mass will accelerate in the direction in which the force acts.

3. The Third Law States. To every action there is an equal and opposite reaction.

The function of any propeller or gas turbine engine is to produce THRUST, (or a propulsion force), by accelerating a mass of air or gas rearwards. If we apply Newton's Laws of Motion to aircraft propulsion it can be said that:-

• a FORCE must be applied in order to accelerate the mass of air or gas: first law,

the acceleration of the mass is proportional to the force applied: second law,

• there must be an equal and opposite reaction, in our case this is THRUST, a forward acting force: third law.