grav fields

Newtons law of gravitation

Any two point masses separated by a distance r attract each other with a gravitational force that’s proportional to the product of their masses and inversely proportional to the square of their separation

Field line rules

Represent magnitude and direction of force per unit mass at that point in the field

Always towards centre of mass

Uniform at surface : parralel to each other , perpendicular to surface , equidistant space between them

Keplers 3rd law

T ² is proportional to r³

Resultant field

Neutral point is closer to object if heavier mass

Synchronous orbits

Equal time period to rotational time period of planet being orbited

Geostationary orbit definition

Remains vertically above the the same point of the equator at all times

Geostationary orbit Features

Same time period as earths rotation (24hrs)

Orbit in equatorial plane

Move in the same direction as earths rotation

Geostationary orbit Uses

satellite television broadcasting

telecommunications transmissions

Geostationary orbit advantages

Maintain continuous contact with satellite and area

Geostationary orbit Disadvantages

Restricted area covered by each satellite - would need many to cover whole earth

Low polar orbits

Passes above north and south poles during each complete orbit

Low polar orbits advantages

Can scan Earth in just a few days

Closer to earth

Greater speed , multiple orbits per day

Low polar orbits disadvantage

Affected by atmosphere so speed can be reduced by air resistance

Low polar orbit uses

Mapping land features

Tracking cloud coverage

Military surveillance

Monitoring ocean currents

Escape velocity

Minimum velocity required to at the surface of a planet in order to escape the gravitational pull of the planet using its own kinetic energy

what is g

gravitational field strength , force on a unit mass at the earths surface

What is G

gravitational constant , relates to the force of attraction between two masses & their separation

Total energy of an orbiting satellite equation

Escape velocity equation

Orbital time period equation

Gravitational force equation

Gravitational field strength equation

Orbital speed equation

Gravitational potential equation

Properties of a radial gravitational field

Field strength is inversely proportional to the distance squared

Region where mass experiences force due to another mass

Non contact force