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Edexcel GCSE Physics Topic 3 + 8 - Conservation of Energy + Forces doing Work
Edexcel GCSE Physics Topic 4 + 5 - Waves + Light and the Electromagnetic spectrum
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Astronomy
The Solar System consists of the Sun (our star), eight planets and their natural satellites (such as our
Moon); dwarf planets; asteroids and comets.
A solar system is defined as a star and all the objects that orbit around it.
Describe the Geocentric Model of the Solar System.
Everything orbits around the Earth. (Geo=Earth Centric = at
centre)
Describe the Heliocentric Model of the Solar System.
Everything orbits around the Sun. (Helio=Sun Centric = at
centre)
Explain which of the models above was supported by
Galileo’s observations. Heliocentric as moons orbit planets
not Earth and planets do not orbit Earth in perfect circles
Compare and contrast the Geocentric/heliocentric models.
Similarities: Circular orbits, number of planets, stars fixed in position
Differences: What is at centre of Universe, Geocentric: Planets follow small circles in their orbits
This is a long exposure image of the night sky centred on the pole star which lies above
the North Pole. Hence the entire sky appears to rotate around the pole star leading
to the belief in the geocentric model
Telescopes are used in space: atmosphere distorts image
due to clouds and dust; atmosphere absorbs x-rays,
gamma-rays and some radio waves, microwaves and
infrared.
Computers are used in improving astronomical
Optical telescopes observe visible light from space. observations because they can be used to
However, they can only be used in the dark and in good analyse images captured by telescopes.
weather.
Radio telescopes detect radio waves coming from space.
Although they are usually very large and expensive they
can be used in bad weather and in both daytime and
nightime
Space telescopes can observe the whole sky and can
operate both night and day. However, they are difficult
and expensive to launch and maintain; if something goes
wrong they can only be fixed form space.
Very Useful Acronym
My Very Eager Mother Just Served Up Nachos
Mercury, Venus, Earth, Mara, Jupiter, Saturn, Uranus, Neptune
, How are orbits analysed?
The weight of an object is the force on it caused by the gravity due to the planet. The weight of an object
and the gravitational field strength are directly proportional. For a given mass, the greater the gravitational
field strength of the planet, the greater its weight.
Gravitational field strength tells us the
weight = mass × gravitational field strength force experienced by a 1kg mass in a
W = mg gravitational field.
This is when: It increases with the mass of a planet,
moon or star. It decreases when the radius
• weight (W) is measured in newtons (N) of a planet, moon or star increases.
• mass (m) is measured in kilograms (kg)
• gravitational field strength (g) is measured in newtons per kilogram (N/kg)
A satellite is an object that orbits a larger
object in space e.g. moon, planets
The centre of mass is where:
- the weight appears to act
- the point at which the mass appears
to be concentrated
Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from
the sun
Comets go around the Sun in a highly elliptical orbit.
The red circle represents the orbit of one of terrestrial planets. As can be seen,
the path of the comet is much more elliptical.
Describe 3 different orbits for artificial satellites. Low circular orbits;
Geostationary - circular high above a fixed point on equator; Highly elliptical.
For the orbits listed, link the orbit to the type of satellite use.
Low polar : spying/mapping as close to surface cover entire Earth.
Low circular: provides high bandwidth and low communication latency.
Geostationary : various forms of telecommunication, including television.
Highly elliptical: communications satellites
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