PHYSICS IGCSE EDEXCEL ALL PAPER 1

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1

speed

distance/time

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acceleration

change in velocity/time taken

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speed in a distance time graph

gradient

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acceleration in a velocity time graph

gradient

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distance in a velocity time graph

area

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weight

mass x gravitational field strength

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scalar

magnitude only

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vector

magnitude and direction

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friction

force that opposes motion, present if an objet is in motion

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stopping distance

thinking distance + braking distance

  • faster speed increases both

  • larger mass increases braking distance

  • slower reaction time increases thinking distance

  • increased grip decreased braking distance

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terminal velocity

weight is equal to drag meaning resultant force is zero, therefore acceleration is 0

<p>weight is equal to drag meaning resultant force is zero, therefore acceleration is 0</p>
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hooke’s law

extension of a helical spring is direction proportional to the applied force

  • there is an elastic limit where elastic behaviour turns into plastic behaviour

  • elastic behaviour: if the applied force is removed, the object will return back to its original shape

  • plastic behaviour: if the applied force is removed, the object will not return back to its original shape, therefore it is deformed

<p><strong>extension of a helical spring is direction proportional to the applied force</strong></p><ul><li><p>there is an elastic limit where elastic behaviour turns into plastic behaviour</p></li><li><p><span>e</span>lastic behaviour: if the applied force is removed, the object will return back to its original shape</p></li><li><p>plastic behaviour: if the applied force is removed, the object will not return back to its original shape, therefore it is deformed</p></li></ul>
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newton’s laws of motion

  1. if resultant force on an object = 0, it will remain at its current velocity (incl. 0 – standing still)

    • inertia means no resultant force/ object will continue doing what it’s doing

    • zero acceleration

  2. object accelerates in the direction of the resultant force

    • speed can remain constant but direction changes, meaning a changed velocity

  3. if object A exerts a force on object B, then object B exerts an equal and opposite force on object A

    • requirements: 1) same type of force, 2) acts on two different objects

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moments

  • moment = force x perpendicular distance from pivot

  • newton metres = newtons x metres

  • principle of moments: sum of clockwise moments equals sum of anticlockwise moments in order for a lever to be in equilibrium

  • in order for lever to be in equilibrium, f1x = f2y

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insulation

to stop the flow of electricity

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conduction

to allow the flow of electricity

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double insulation

covering a metal object in plastic, therefore it acts as an insulator

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earthing

carries excess current into the earth through a metal rod put into earth

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19

circuit breakers

switch opens, therefore breaking the circuit if too much current is flowing through

  • benefit: reusable

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20

mains electricity

230V

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fuse

melts if current gets too high therefore breaking the circuit

  • drawback: one time use; after it melts it must be replaced

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ammeter

measures current, must be placed in series

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voltmeter

measures voltage, must be placed in parallel around the component under test

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a.c. supply

current is constantly changing direction

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d.c. supply

current keeps flowing in the same direction

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voltage

current x resistance

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metal filament lamp

as temperature increases, resistance increases

<p>as temperature increases, resistance increases</p>
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wire

current through a wire is proportional to voltage

<p>current through a wire is proportional to voltage</p>
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diode

current in a diode only flows through in one direction

<p>current in a diode only flows through in one direction</p>
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LEDs

emit light when current flows through them in the forward direction

  • used in remote controls, digital clocks, traffic lights

  • don’t have a filament that can burn out

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LDRs

changes resistance depending on how much light falls on it

  • in bright light, resistance decreases

  • in darkness, resistance increases

<p>changes resistance depending on how much light falls on it</p><ul><li><p>in <strong>bright light</strong>, resistance decreases</p></li><li><p>in <strong>darkness</strong>, resistance increases</p></li></ul>
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thermistors

temperature-dependent resistor

  • in hot conditions, resistance decreases

  • in cool conditions, resistance increases

<p>temperature-dependent resistor</p><ul><li><p>in <strong>hot</strong> conditions, resistance decreases</p></li><li><p>in <strong>cool</strong> conditions, resistance increases</p></li></ul>
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series circuits

  • in series, voltage is split between components

    • E.g. power source is 6V, both lightbulbs have 3V (assuming they have the same resistance)

  • the current is the same everywhere in a series circuit

  • benefit: more simple (less wires required)

  • negative: components have a greater resistance

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parallel circuits

  • in parallel, voltage is equal in components

    • E.g. power source is 6V, both lightbulbs have 6V (assuming they have the same resistance)

  • at a junction, current is conserved

    • current is split between branches in a parallel circuit

  • benefit: if one component breaks, the others will continue running

  • negative: while the bulbs may be brighter, the power source would drain faster

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current

  • current = charge/time

  • definition: rate of flow of charge

  • current is conserved at a junction

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voltage

  • voltage = energy/charge

  • definition: energy transferred per charge

  • 1 volt = 1 joule/coulomb

<ul><li><p>voltage = energy/charge</p></li><li><p>definition: <strong>energy transferred per charge</strong></p></li><li><p>1 volt = 1 joule/coulomb</p></li></ul>
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transverse waves

vibrations perpendicular to energy transfer

<p><span>vibrations perpendicular to energy transfer</span></p>
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longitudinal waves

vibrations parallel to energy transfer

<p><span>vibrations parallel to energy transfer</span></p>
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wave speed

λ x frequency

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frequency

1/time

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doppler effect

  • wavefronts are further apart, therefore meaning a longer wavelength

  • wavelength is inversely proportional to frequency

  • longer wavelength means a lower frequency, meaning a lower pitch

  • wave speed is constant

  • V = λf, if wavelength is longer so frequency must be lower to maintain the same wave speed

<ul><li><p>wavefronts are further apart, therefore meaning a longer wavelength</p></li><li><p>wavelength is inversely proportional to frequency</p></li><li><p>longer wavelength means a lower frequency, meaning a lower pitch</p></li><li><p>wave speed is constant</p></li><li><p>V = λf, if wavelength is longer so frequency must be lower to maintain the same wave speed</p></li></ul>
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refraction

when a wave passes a boundary between two different density media, it changes speed and sometimes direction too

  • from more to less optically dense, wave goes away from the normal

  • from less to more optically dense, wave goes towards the normal

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electromagnetic spectrum

radio waves → microwaves → infrared → visible light → ultraviolet → x-rays → gamma rays (increasing f, decreasing λ)

radio waves -> communication

microwaves -> cell phones, however heats internal tissues

infrared -> cooking food, night vision/thermal imaging, however can cause skin burns

visible light -> photography

ultraviolet -> testing fake bank notes, sterilisation, however may cause skin cancer by the mutation of skin cells

x-rays -> view internal structure of our bodies, however may cause cancer by the mutation of cells

gamma rays -> sterilise medical equipment, however may cause cancer by the mutation of cells

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graphical method

  1. take multiple incidences and refractions,

  2. plot a graph of sin (i) against sin (r)

  3. draw a straight line of best fit (should be directly proportional)

  4. find gradient of line

  5. to find n, gradient = diff in y/ diff in x

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critical angle

  • if incidence is greater than C, all rays will be totally internally reflected

  • MUST take place at a boundary from a substance that is more optically dense to a substance that is less optically dense

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total internal reflection

knowt flashcard image
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sound waves

  • humans can only hear sound waves from 20 – 20,000 Hz

  • sound waves are longitudinal waves

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energy stores

kinetic, thermal, chemical, gravitational potential, elastic potential, electrostatic, magnetic, nuclear

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principle of conservation of energy

energy can be stored, transferred between stores or dissipated - but it can never be created or destroyed

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efficiency

useful/total x 100

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sankey diagrams

knowt flashcard image
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radiation energy transfer

  • thermal radiation is infrared radiation consisting of plenty of EM waves

  • an object that is hotter than its surroundings emits more radiation than it absorbs

  • an object that is cooler than its surroundings absorbs more radiation than it emits

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conduction energy transfer

  • mainly in solids

  • vibrating particles transfer energy from their kinetic energy store to the kinetic energy store of neighbouring particles

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convection energy transfer

  • in liquids and gases

  • more energetic particles move from a hotter region to a cooler region, transferring energy as they do

  • convection currents are all about changes in density

<ul><li><p>in liquids and gases</p></li><li><p>more energetic particles move from a hotter region to a cooler region, transferring energy as they do</p></li><li><p>convection currents are all about <strong>changes in density</strong></p></li></ul>
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colours in energy transfer

black → good absorber, bad reflector

white → good reflector, bad absorber

matte → good absorber

shiny → good reflector

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work done

force x distance moved

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kinetic energy store

KE = ½ x mass x speed²

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density

mass/volume

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pressure

force/area

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absolute zero

-273 degrees celsius

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particle collision theory

colliding gas particles create pressure

  • as gas particles move, they randomly collide into each other

  • they exert a force and their momentum and direction change

  • pressure created depends on speed and frequency

  • increasing temperature increases pressure

  • increasing volume decreases pressure

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magnetic fields

region where magnetic materials experience a force

  • magnetic field lines show size and direction of magnetic fields, always from north to south

    1. north to south

    2. at least 3 lines

    3. field lines closer at poles

<p>region where magnetic materials experience a force</p><ul><li><p>magnetic field lines show size and direction of magnetic fields, always from north to south</p><ol><li><p>north to south</p></li><li><p>at least 3 lines</p></li><li><p>field lines closer at poles</p></li></ol></li></ul>
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magnetic materials

material that will turn into a magnet if it is brought into a magnetic field

  1. iron

  2. cobalt

  3. nickel

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magnetically hard

permanently magnetised, difficult to magnetise and demagnetise

  • e.g. steel

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magnetically soft

temporarily magnetised, easy to magnetise and demagnetise

  • e.g. iron

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uniform field

  1. evenly spaced

  2. parallel

  3. arrow from north to south

<ol><li><p>evenly spaced</p></li><li><p>parallel</p></li><li><p>arrow from north to south</p></li></ol>
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magnetic induction

when a magnetic material is brought into a magnetic field, it becomes a magnet (gets magnetised)

  • if brought to north pole, the side closest to the north pole will become the south pole

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iron filings

  1. place a white piece of paper over a bar magnet

  2. sprinkle iron filings on top

  3. gently tap the paper until magnetic field lines appear

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compass

  1. place multiple needle compasses around a bar magnet

  2. needle of compass will align with the magnetic field

  3. this will show the direction of the magnetic field

<ol><li><p>place multiple needle compasses around a bar magnet</p></li><li><p>needle of compass will align with the magnetic field</p></li><li><p>this will show the direction of the magnetic field</p></li></ol>
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solenoid

when current flows through a current-carrying wire, it produces a magnetic field

  1. magnetic field inside a current-carrying solenoid is uniform and strong

  2. outside the bar, the field is one just like a magnet

  3. ends of solenoid act as the north and south poles

<p><span>w</span>hen current flows through a current-carrying wire, it produces a magnetic field</p><ol><li><p>magnetic field inside a current-carrying solenoid is uniform and strong</p></li><li><p>outside the bar, the field is one just like a magnet</p></li><li><p>ends of solenoid act as the north and south poles</p></li></ol>
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fleming’s left hand rule

  1. current flowing through a wire produces a magnetic field

  2. this magnetic field interacts with the magnetic field of the permanent magnet

  3. this produces a force

<ol><li><p>current flowing through a wire produces a magnetic field</p></li><li><p>this magnetic field interacts with the magnetic field of the permanent magnet</p></li><li><p>this produces a force</p></li></ol>
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motor effect

loudspeakers

  • current-carrying wire produces magnetic field

  • A.C. current, meaning a current that changes direction continuously

  • this magnetic field interacts with the magnetic field of a permanent magnet

  • this produces a force -> every time the direction of the current changes, the direction of the force changes as well

  • frequency of vibration correlates to the frequency of sound

<p>loudspeakers</p><ul><li><p>current-carrying wire produces magnetic field</p></li><li><p>A.C. current, meaning a current that changes direction continuously</p></li><li><p>this magnetic field interacts with the magnetic field of a permanent magnet</p></li><li><p>this produces a force -&gt; every time the direction of the current changes, the direction of the force changes as well</p></li><li><p>frequency of vibration correlates to the frequency of sound</p></li></ul>
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factors that speed up a D.C. electric motor

  1. more current

  2. more turns in the coil

  3. stronger magnetic field

  4. soft iron core in the coil

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electromagnetic induction

the creation of a voltage in a wire which is experiencing a change in magnetic field

  • dynamo effect → using electromagnetic induction to generate electricity using energy from kinetic energy stores

    • to get a bigger voltage, increase

      1. strength of magnet

      2. number of turns on coil

      3. speed of movement

<p>the creation of a voltage in a wire which is experiencing a change in magnetic field</p><ul><li><p>dynamo effect → using electromagnetic induction to generate electricity using energy from kinetic energy stores</p><ul><li><p>to get a bigger voltage, increase</p><ol><li><p>strength of magnet</p></li><li><p>number of turns on coil</p></li><li><p>speed of movement</p></li></ol></li></ul></li></ul>
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structure of an atom

  • neutron number = mass - proton

  • isotopes: same proton number but different number of neutrons

  • proton

    • mass 1

    • charge +1

  • neutron

    • mass 1

    • charge 0

  • electron

    • mass 1/1000

    • charge -1

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alpha radiation

  • helium nucleus

  • lowly penetrating

  • highly ionising

  • emitting an alpha particle causes proton number to decrease by 2, mass number decreases by 4

<ul><li><p>helium nucleus</p></li><li><p>lowly penetrating</p></li><li><p>highly ionising</p></li><li><p>emitting an alpha particle causes proton number to decrease by 2, mass number decreases by 4</p></li></ul>
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beta radiation

  • electron

  • moderately penetrating

  • moderately ionising

  • emitting a beta particle causes proton number to increase by 1, mass number stays the same

<ul><li><p><span>e</span>lectron</p></li><li><p>moderately penetrating</p></li><li><p><span>m</span>oderately ionising</p></li><li><p>emitting a beta particle causes proton number to increase by 1, mass number stays the same</p></li></ul>
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gamma radiation

  • electromagnetic wave

  • no mass, just energy

  • highly penetrating

  • lowly ionising

  • always happens after an alpha or beta decay

  • emitting gamma rays have no effect on the proton and mass number

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neutron radiation

  • emitting a neutron causes proton number to stay the same, mass number decrease by 1

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measuring radioactivity of a sample

  1. measure background radiation using a GM detector (Bq)

  2. measure Bq reading from a known distance (control) to radioactive source

  3. subtract background radiation reading from total Bq reading

  4. repeat 3 times and average concordant results, remove anomalies

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half-life

time taken for half of the radioactive nuclei to decay

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nuclear fission

splitting of a large parent nucleus into smaller daughter nuclei and neutrons which collide with other nuclei, causing a chain reaction

<p><span>s</span>plitting of a large parent nucleus into smaller daughter nuclei and neutrons which collide with other nuclei, causing a chain reaction</p>
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nuclear fusion

two small nuclei collide and fuse to create a larger, heavier nucleus

  • conditions → extremely high temperature (high kinetic energy) and pressure (to overcome electrostatic repulsion of like charges)

<p><span>t</span>wo small nuclei collide and fuse to create a larger, heavier nucleus</p><ul><li><p>conditions → extremely high temperature (high kinetic energy) and pressure (to overcome electrostatic repulsion of like charges)</p></li></ul>
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nuclear reactors

  • moderator (usually graphite or water) slows down neutrons

  • control rods (usually boron) limit rate of fission by absorbing excess neutrons

  • shielding (usually thick concrete) used to absorb ionising radiation

  • substance (usually CO2) pumped around to transfer energy to water in the heat exchanger

<ul><li><p>moderator (usually graphite or water) slows down neutrons</p></li><li><p>control rods (usually boron) limit rate of fission by absorbing excess neutrons</p></li><li><p>shielding (usually thick concrete) used to absorb ionising radiation</p></li><li><p>substance (usually CO2) pumped around to transfer energy to water in the heat exchanger</p></li></ul>
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uses of nuclear radiation

  1. medical tracers

    • radioactive source has to have a short half-life

  2. sterilisation

    • of food and equipment

  3. treating cancer

    • ionising radiation can kill or damage cells and tissues

  4. industrial tracers and thickness gauges

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risks of nuclear radiation

  1. ionising radiation can damage cells and tissues

    • beta and gamma radiation can penetrate the skin and soft tissues

    • radiation collides with molecules in cells causing ionisation which damages or destroys molecules

  2. irradiation

    • exposure to radiation

    • keeping sources in lead-lined boxes reduces risk of irradiation

  3. contamination

    • radioactive particles getting onto objects

    • use gloves and tongs when handling sources

  4. disposal

    • radioactive sources are difficult to dispose of

    • seal into glass blocks which are then sealed in metal canisters and buried underground

    • site must be geologically stable

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universe

large collection of billions of galaxies

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galaxy

large collection of stars

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orbits

  • planets orbit the sun

  • comets orbit the sun

  • asteroids orbit the sun

  • moons orbit planets

elliptical orbit (elongated) → comets

circular orbit → planets

gravitational field strength affected by:

  1. mass → higher mass higher g

  2. distance → less distance higher g

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orbital speed

2 x π x orbital radius/time period

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stellar evolution

stars much bigger than the sun: nebula → protostar → main sequence star → red supergiant → supernova → neutron star or black hole

stars around the same size as the sun: nebula → protostar → main sequence star → red giant → white dwarf

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star colour

(hottest) blue → white → yellow → orange → red (coolest)

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