Physics ~ P1


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  • Created by: Lucy
  • Created on: 30-12-11 10:52

Solar system

8 planets orbit the sun in elipses.

Sun   Mercury   Venus    Mars     Asteroid belt   Jupiter   Saturn    Uranus   Neptune


               Inner planets                                                        Outer planets

Other things that orbit the sun: dwarf planets, comets (balls of rock, dust and ice) and dust.

Sun's and other stars energy comes from nuclear fusion - when hydrogen nuclei join together to make helium. Gives off massive amounts of heat and light.

Earth:       5 000 million years old

Sun:         5 000 million years old

Universe: 14 000 million years old

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Light year: The distance that light travels through a vacuum in one year. Measure of DISTANCE.

Parallax: When something appears to move when you look at it from different places. This can be used when working out how far away a star is. Stars that are far away have less apparent movement than close stars.

Red shift: When a galaxy is moving away from us the wavelength of the light from it becomes redder.

Amplitude: The distance from the rest position to the crest or trough. The bigger the amplitude, the more energy the wave has.

Frequency: The number of complete waves passing a certain point per second.

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We see stars as they were in the past. The further away the star the longer it takes for the light from it to reach us and the longer it takes for us to see it, eg. If a star was 4.2 light years away, the light from it would take 4.2 years to reach us - this means we would see it as it was 4.2 years ago.

From observations of red shifts of different galleries we know that: The more distant the galaxy, the faster it moves away from us - the whole Universe is expanding.

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Alfred Wegener's Theory of Continental Drift

His theory:

Africa and South America had previously been one continent which had been split by continental drift. He proved this by finding that there were matching layers in the rocks on the continents, and similar fossils in both South America and South Africa.

300 million years ago there had been just 1 'supercontinent' which he called Pangaea. Pangaea broke into smaller chunks which are the continents today which are still moving and changing.

It wasn't accepted at first because:

1. Explained things couldn't be explained by the 'land bridge' theory and reaction from other scientists was hostile.

2. His explanation of how the 'drifting' happened wasn't convincing as the movement wasn't detectable.

3. He wasn't a 'proper' geologist, he was a meteorologist.

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Sea floor Spreading

At the Mid-Atlantic ridge which runs the whole length of the Atlantic, magma rises up through the sea floor, solidifies and forms underwater mountains that are roughly symmetrical either side of the ridge. This is called sea floor spreading.

The magnetic orientation of rocks shows that the continents are moving apart. As the liquid magma erupts out of the gap, iron particles in the rocks tend to align themselves with the Earth's magnetic field - as they cool they set in position. Every half million years the Earth's magnetic field swaps direction.

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Solid Inner core


Liquid outer core

Tectonic Plates:

The crust and the upper part of the mantle are cracked into a number of large pieces called tectonic plates. Convection currents in the mantle, caused by heating in the core and mantle, cause the plates to drift. The plates are moving at speeds of a few cm per year. Earthquakes often happen near the edges of plates. Volcanoes form at the boundaries between two tectonic plates. Mountains form when plates crash into each other.

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Seismic Waves

Seismic waves all over the surface of the planet are recorded using seismographs.

There are two different types of seismic waves that travel through the earth:


P-waves travel through solids and liquids.

They travel faster than S-waves.

P-waves are longitudinal.


S-waves only travel through Solids.

They are Slower than P-waves.

S-waves are transverse.

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The distance a wave has travelled is worked out by using the formula:

distance = speed x time

    (m)         (m/s)     (s)

1 Hz is 1 wave per second

The wave speed is worked out by using the formula:

speed = Frequency x Wavelength

 (m/s)          (Hz)               (m)

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