Aerofoil: Any surface, as a wing, aileron, or stabiliser, designed to aid in lifting or controlling an aircraft by making use of the air currents through which it moves.

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Amplitude: The absolute value of the maximum displacement from a zero value during one period of oscillation.

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Angular velocity: The time rate of change of angular position of a rotating body, usually expressed in radians per second or radians per minute.

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Boomerang: A bent or curved piece of tough wood used by the Australian Aborigines as a throwing club, one form of which can be thrown so as to return to the thrower.

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Centripetal force: The force, acting upon a body moving along a curved path, that is directed toward the centre of curvature of the path and constrains the body to the path.

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Combustion: The act or process of burning.

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Counterweight: A weight used as a counterbalance.

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Deep space: Space beyond the limits of the solar system.

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Displacement: The linear or angular distance in a given direction between a body or point and a reference position.

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Doppler effect: The shift in frequency of acoustic or electromagnetic radiation emitted by a source moving relative to an observer as perceived by the observer: the shift is to higher frequencies when the source approaches and to lower frequencies when it recedes.

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Electric current: The time rate of flow of electric charge, in the direction that a positive moving charge would take and having magnitude equal to the quantity of charge per unit time – measured in Amperes.

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Escape velocity: The minimum velocity that an object at a given distance from a gravitating body must have so that it will continue to move away from the body instead of orbiting about it.

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Equilibrium: A state of rest or balance due to the equal action of opposing forces.

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 Gyroscopic precession: A phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied.

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Infrared: The part of the invisible spectrum that is contiguous to the red end of the visible spectrum and that comprises electromagnetic radiation of wavelengths from 800nm to 1mm.

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Internal energy: A function of thermodynamic variables, such as temperature, that represents the internal state of a system that is due to the energies of the molecular constituents of the system.

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Kinematics: The branch of mechanics that deals with pure motion, without reference to the masses and forces involved.

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Kinetic energy: The energy of a body or a system with respect to the motion of the body or of the particles in the system.

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Microwave: An electromagnetic wave of extremely high frequency, 1 GHz or more, and having wavelengths of from 1mm to 30cm.

 

Moment of inertia: The moment of inertia of a point mass with respect to an axis is defined as the product of the mass times the distance from the axis squared. The moment of inertia of any extended object is built from that basic definition. The general form of the moment of inertia involves an integral.

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Nuclear warhead: A warhead containing a fission or fusion bomb.

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Photon: A quantum of electromagnetic radiation, usually considered as an elementary particle that is its own antiparticle and that has zero rest mass and charge and a spin of one.

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Plasma: A highly ionised gas containing an approximately equal number of positive ions and electrons.

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Projectile: A body projected or impelled forward, as through the air.

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Radar: A device for determining the presence and location of an object by measuring the time for the echo of a radio wave to return from it and the direction from which it returns.

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Radio: The part of the electromagnetic spectrum which encompasses wavelengths between 1mm and 30,000m.

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Relativistic: Having a magnitude that is a significant fraction of the speed of light.

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Reynold’s number: The ratio of internal forces to viscous forces.

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Resistive forces: A force whose direction is opposite to the velocity of the body, or the sum of the other forces.

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Shock wave: A region of abrupt change of pressure and density moving as a wave front at or above the velocity of sound, caused by an intense explosion or supersonic flow over a body.

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Sonic boom: A loud noise caused by the shock wave generated by an aircraft moving at supersonic speed.

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Supersonic: Speed greater than that of sound through air.

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Tension: The deformation of an elastic body that results in its elongation.

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Ultrasonic: Sound with a frequency greater than 20,000 Hz, approximately the upper limit of human hearing.

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Wavefront: A surface, real or imaginary, that is the locus of all adjacent points at which the phase of oscillation is the same.