Definitions - P21 Gravitational Fields

Gravitational force

Gravitational force

A force that is always attractive and is excreted between objects due to their masses. A non contact force

Force field

An area in which an object experiences a non contact force

Gravitational field lines

Represent the direction of force on a mass

Uniform field

Exerts the same gravitational force on a mass everywhere in the field

Radial field

The force exerted depends on the position of the object in the field

Gravitational field strength

The force per unit mass exerted by a gravitational field on an object. This value is constant in a uniform field but varies in a radial field. It is proportional to the product of the masses and inversely proportional to the distance squared

Newtons law of gravitation

The magnitude of the gravitational force between two masses is directly proportional to the product of the masses and is inversely proportional to the square of the distance between them

Gravitational field strength in a radial field

Follows the inverse square relationship between the distance and the force. Acts as a centripetal force which causes a centripetal acceleration (circular motion)

Gravitational potential

The work done per unit mass to move a small object (point mass) from infinity to the point or Work done. This value is always negative.

Synchronous orbit

The orbital period of the satellite is equal to the rotational period of the object that it is orbiting

Geostationary orbit

Follows a specific geosynchronous orbit, meaning their orbit period is 24 hours and they always stay above the same point on the earth - directly above the equator

Keplers first law

Each planets orbit around the sun is an ellipse. The suns centre is always at one focus point. The suns distance from the planet is constantly changing as the planet goes round it’s ellipse.

Keplers second law

Any two areas on the orbit of a planet will be equal in size across the same time period.

Keplers third law

R cubed is directly proportional to T squared. The division of these two is a constant

Escape velocity

The minimum velocity necessary to leave a gravitational field of a planet or large mass