Please enable JavaScript.
Coggle requires JavaScript to display documents.
Fields (Gravitational (Orbits (Geostationary Satellites (Geosynchronous…
Fields
Gravitational
Orbits
Low Earth Satellites
Orbit close to the Earth, and so have a greater angular speed than the Earth, and so move relative to a point on the Earth's surface
They are cheap to launch, and don't need very powerful transmitters, however you need many to maintain full coverage, and you need a tracking station to track the motion of the satellite across the sky, to communicate with it
They can image in high detail making them useful for mapping, monitoring, imaging and weather purposes
Polar Satellites
-
They can have a higher angular speed than the Earth, so will constantly be over new parts of the Earth (in both latitude and longitude) with each orbit
-
-
Geostationary Satellites
Geosynchronous Satellites
Have a time period of 24 hours so will be over the same part of the Earth at the same time each day
Have a time period of 24 hours, orbit in the same direction as the Earth, orbit above the equator, and so stay stationary relative to a point over the equator
There is only one particular radius orbit that allows this, and geostationary satellites need to have very powerful transmitters to send signals back to the Earth over the long distances involved
Stay stationary relative to Earth's surface, so they can be used to send signals to static receivers, and one satellite can cover a large area due to large radius of orbit
Useful in communications, radio and TV
-
In a circular orbit the kinetic energy of the satellite remains constant as the centripetal force acting on it is perpendicular to it's direction of motion and so no work is done on the satellite
Newton's Law of Universal Gravitation
The magnitude of the force of attraction between two objects with mass is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
-
Gravitational Field Strength \(g\)
The force acting per 1kg of mass at a point in a gravitational field
-
Gravitational Potential Energy \(U\)
(About a point mass) The work done against gravity in bringing a 1kg mass from an infinite distance away from the field, to a given point in the field
-
Gravitational Potential \(V\)
The potential energy of a 1kg mass at a point in the field,
or
The work done against the field in moving a 1kg mass from an infinite distance away to a point in the field
-
Escape velocity is the speed you would have to give to an unpowered object in order for it to have enough energy to escape a gravitational field and never fall back into the gravitational well
Electric
Coulomb's Law
The magnitude of the force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them, with like charges repelling and opposite charges attracting
-
Electric Field Strength \(E\)
The force acting per 1C of positive charge at a point in an electric field
-
Electric Potential Energy \(U\)
(About a point charge) The work done against the electric field in bringing the charge from an infinite distance away from the field to a point in the field
-
Electric Potential \(V\)
The potential energy of 1C of positive charge at a point in an electric field
or
The work done against the field in bringing 1C of positive charge from an infinite distance away from the field to a point in the field
-
Conducting Spheres
A sphere with charge evenly distributed over it's surface can be considered as a point charge, with all the charge on it's surface concentrated at it's centre
-
Uniform Electric Fields
Can be created by placing two parallel plates next to each other, with a potential difference between them
-
The approximation works best near the centre of the plates, as towards the edges the field lines start to move outwards and curve
-
-
-