Ask Elton
Your Flight Training & Ground School Specialist

PPL » Aircraft Tech Knowledge (A) » Definitions, Terminology, Units and Abbreviations

12.2 Definitions, Terminology, Units and Abbreviations

12.2.2 State the International System (SI) and ICAO units used to express:

(a) distance;


  • metre (m)



(b) time;


  • second (s)



(c) velocity;


  • metres/second (m/s)



(d) mass;


  • kilogram (kg)



(e) volume;


  • cubic metre (m³)



(f) temperature;


  • kelvin (K)
    • when measured from absolute zero


  • The degree Celsius (ºC)
    • when measured from the freezing point of water



(g) altitude.


  • feet (ft)



12.2.4  Define and where appropriate show the relevant relationships between:

(a) mass, weight and gravitational force (g);


Mass (m)

  • the amount of matter in an object. 
  • 1kg of mass on the earth is the same as 1kg of mass on the moon.


Gravitational Force (g)

  • is the force of attraction between two objects due to their masses and the distance between them.
  • the bigger the object, and the closer the distance, the bigger the force.
  • Earth has a value of 9.81 m/s² at its surface.
  • The Moon has a value of 1.62 m/s²


Weight (W)

  • the force produced by gravitational attraction between masses.
  • Weight = mass x gravity (W = mg)
  • because the earth is larger than the moon, 1kg of mass is heavier on the earth than on the moon.


(b) inertia;


  • A property of matter by which it continues in its existing state of rest or uniform motion in a straight line.
  • More mass = more inertia.
  • Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.
To see more, you must subscribe for licence "PPL" or sesssion "Aircraft Tech Knowledge (A)"