Basic concepts of aerodynamics

NEWTON LAWS

1ª The Inercia law : An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

2ª Newton’s second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables – the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased.

3ª  For every action, there is an equal and opposite reaction.

The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs – equal and opposite action-reaction force pairs.

HYDROSTATICS EQUATION

As you know we don´t have  to learn this formula but it is interesting to understand it, because it is the basement to explain the lift force.

SPEED OF SOUND & MACH NUMBER

Speed of sound mainly depends  on the temperature 

Co it is the speed of sound at see level , in I.S.A conditions.

• MACH NUMBER ( MN) it is the relationship between the true air speed and the speed of sound.

          The higher we fly the lower temperature we have so the speed of sound decreases.               That´s why the mach number increases.

          MN<0.5  The air is considered incompressible

          MN<1 Subsonic

          MN=1 Sonic

          MN>1 Supersonic