# Physics Definitions

Field Vector

A field vector is a single vector that describes the strengths and direction of a uniform vector field. For a gravitational field, the field vector is g Weight

Weight is defined as the force on a mass due to the gravitational field of a large celestial body such as the Earth Gravitational Potential Energy

Gravitational Potential Energy is the energy of a mass due to its position within a gravitational field. On a large scale GPE is defined as the work done to move an object from infinity to a point within a gravitational field Projectile

A projectile is any object launched into the air

Trajectory

The trajectory of a projectile is the path that it follows during its flight Escape Velocity

Escape Velocity is the initial velocity required by a projectile to rise vertically and just escape the gravitational field of a planet Thrust

Thrust is a force that is exerted on an object by the expulsion or acceleration of mass in one direction Uniform Circular Motion

Uniform Circular Motion is the circular motion with a uniform orbital speed Centripetal Force

Centripetal force is the force that acts to maintain circular motion and is directed towards the centre of the circle Centripetal Acceleration

Centripetal Acceleration is always present in uniform circular motion it is associated with centripetal force and is also directed at the centre of the circle Period

Period is the time taken to complete on orbit

Low Earth Orbit

Low Earth Orbit is an orbit higher than 250km and lower than 1000km Geostationary Orbit

Geostationary Orbit is an orbit where the Satellite orbits in tandem with that of earth. This corresponds to an approximate altitude of 35 800km Transfer Orbit

Transfer Orbit is a orbit used to manoeuvre a satellite from one orbit to another Ionisation Blackout

Ionisation Blackout is a period of no communication with a space craft due to a surrounding layer of ionised atoms forming in the heat of re-entry Vector

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