The weight of an aircraft is applied at the CG. The lift at the CP. The relative position between these 2 points determines the stability of the aircraft. For an Aircraft with a tail surface, a CG in front of the CP constitutes a stable system, while a CG behind the CP an unstable system.

Their formation is most often triggered by freezing water vapour from the exhaust of aircraft engines.

a line extending from the leading edge to the trailing edge equidistent from the upper and lower surface of the aerofoil.

Drag is the component of the total aerodynamic force parallel to the relative airflow.

Drag is generated by any body placed in a flow and it's composed of friction, form, and pressure drag.

A swept wing makes the velocity vector normal to the leading edge a shorter distance than the chordwise resultant.

Alternate air is....

For a commerical aeroplane: During take off. At this point the aircraft has it it's maximum weight, and accelerating in the vertical plane requiring the highest ammount of lift to counteract the weight.

To be the most efficient, aircraft descend at Vmd. Vmd increases with Weight, and therefore the rate of descent increases as well with weight.

Drag penalties (additional weight)

Less controllability

To protect the engine from blowing up as it is easy to open the throttles to far during take off at sea level.