Topic 7 Flashcards
Done
7.1P
Describe the relationship between gravity and the weight of an object
Directly proportional
7.1P
Describe the relationship between the mass of a planet and the gravity acting on it
Directly proportional
(the greater the m the more g will act)
(moon has less m so less gravity)
7.1P
Describe the relationship between radius and surface gravity
Inversely proportional
(Smaller radius -> greater gravity)
7.1P
What factors affect the force of gravitational attraction between 2 objects?
-Mass
-d between the masses
7.2P
What does the solar system consist of?
-Sun (our star)
-8 planets (and their natural satellites e.g. our moon)
-Dwarf planets
-Asteroids
-Comets
7.3P
Recall the names and order of the eight planets from the sun (closest to furthest)
-Mercury
-Venus
-Earth
-Mars
-Jupiter
-Saturn
-Uranus
-Neptune
(My Very Energetic Mother Just Swam Under a Narwhal)
7.3P
a) Name 4 terrestial (rocky) planets
b) Name 2 gas giants
c) Name 2 ice giants
a) Mercury, Venus, Earth, Mars
b) Jupiter, Saturn
c) Uranus, Neptune
7.4P
Describe how ideas about the structure of the Solar System have changed over time
-Geocentric model -> Earth in centre Sun/planets orbits
-Naked eye: Sun/stars/planets revolve around us in same direc (same pattern everyday)
-Heliocentric model -> Planets orbit Sun
-Noticed planets/stars follow pattern throughout yr
-Sun didn’t (movement = slightly diff each day)
7.4P
a) Describe the evidence for the geocentric model
b) Describe the evidence against the geocentric model (so for the heliocentric)
a) -Sun/moon/planets appear to move across sky in same direc -> look like orbit Earth
-Pattern was repeating
b) -Planets e.g. Jupiter have moons which orbit them -> not everything orbits Earth
-Sun movement slightly diff each day
-Planets can appear to move backwards (retrograde motion)
7.5P
Describe the orbit of moons (natural satellites)
Elliptical
7.5P
Describe the orbit of planets
Circular
7.5P
Describe the orbit of comets
Elliptical
7.5P
Describe the orbit of artificial satellites
Elliptical
7.6P
What causes the earth to accelerate?
Gravity of the Sun
7.6P
Explain for a circular orbit how the force of gravity can lead to changing velocity of a planet but unchanged speed
-Constant speed
-Changing direction
-So velocity is changing
7.7P
a) How does the height of an orbit affect the gravitational force on the satellite?
b) How does this affect the speed it must move to stay in the orbit?
c) What would happen if the satellite slowed down?
a) Lower orbit -> greater F
b) If in lower orbit must be faster otherwise will get pulled in
c) Would move to higher orbit
7.7P
Explain why objects with elliptical orbits don’t travel at constant speeds
As get closer to Sun -> More F acts -> faster
7.7P
Why must the radius change if the orbital speed changes for a stable orbit to be possible?
Balance gravitational F (pulling object in) & centripetal F (keeping it in circular path)
7.8P
Compare the Steady State and Big Bang theories
Steady State
-Matter constantly created -> Density always constant
-Universe always existed as it does now
Big Bang
-All matter started as tiny point
-Density of matter decreases over time
Both
-Space is expanding
-Universe started ~13.5 bill years ago
7.9P
State 2 pieces of evidence that support the Big Bang theory
-Red-shift
-CMBR
(Cosmic microwave background radiation)
7.10P
Which model for the origin of the universe is the most accepted and why?
-Big Bang theory
-More evidence
7.11P
Describe the doppler effect
When source moves relative to observer -> change in λ & f of wave for observer
7.11P
How does the pitch of a siren change for an ambulance driver?
It doesn’t
7.11P
Explain how the sound of a siren changes as a fire engine passes an observer
-As approaches observer sound waves compressed (short wavelengths) -> ↑ frequency -> ↑ pitch
-As passes observer long wavelengths -> ↓ frequency -> ↓ pitch
-Doppler effect
7.12P
What is red-shift? How is it measured?
-Light shifts towards red end of spectrum
-Change in wavelength
7.12P
What 2 things does a greater red-shift mean?
-Galaxies moving further away
-Moving faster
7.13P
Explain how red-shift provides evidence for the Universe expanding
-Increase in red-shift
-Shows GALAXIES moving away from Earth
7.14P
Explain how the red-shift of galaxies backs up both the Steady State theory and the Big Bang theory
-Shows galaxies moving away
-SSt: new matter constantly created to maintain constant density as universe expands
-BBt: Supports idea that universe expanding from single point
7.15P
Explain how the discovery of CMBR led to the Big Bang theory becoming the currently accepted model
-CMBR = radiation released at beginning of universe
(Present wherever telescope is pointed)
-Proves universe had hot dense beginning which has expanded since
7.16P 7.18P
Name the stages of the evolution of stars
Nebula -> Main sequence star -> Red giant -> White dwarf
OR
Nebula -> Main sequence star -> Red supergiant -> Supernova -> Neutron star or Black Hole
7.16P
Describe, in detail, the process a nebula goes through to become a white dwarf
-Nebula = cloud of gas
-Gravity pulls gas together -> main sequence star
-H₂ fusion -> heats -> pressure ↑ -> thermal expansion but gravity holds star together -> stable (continues for bill of yrs)
-Eventually H₂ fusion runs out -> star cools -> collapses under gravity (bc outward F due to fusion is less than inward F due to gravity) which makes star hot again
-Helium fusion makes star expand more -> red giant
-Eventually fuel runs out
-Gravity = bigger than thermal expansion -> star collapses -> tiny cold star (almost gives off no light)
7.17P 7.18P
Describe, in detail, the process a nebula goes through to become a neutron star or a black hole
-Nebula = cloud of gas
-Gravity pulls gas together -> main sequence star
-Star fuses -> heats -> pressure ↑ -> thermal expansion but gravity holds star together -> stable
-Eventually H₂ fusion runs out -> star cools -> collapses under gravity which makes star hot again
-Helium fusion makes star expand more -> red supergiant
-Star goes through cycle of collapsing & expanding, helium nuclei fusing heavier metals each time (heaviest metal it can form is iron)
-Thermal expansion reduces equilibrium -> star collapses -> rebounds on its centre (bc gravity is greater) -> star explodes -> supernova
-After supernova, remains form neutron star or black hole
7.18P
Where is the only place elements heavier than iron can be produced?
In a supernova
7.18P
What is a neutron star?
-Neutrons densely packed due to gravity
-Dense centre
7.18P
What is a key feature of a black hole?
Large gravity (not even light can escape)
7.19P
Most space telescopes orbit the Earth but the Spitzer telescope stays behind the Earth to hide from the Sun. Suggest why this is necessary
-Spitzer observes infrared (heat)
-Infrared from Sun would overpower image
7.19P
Describe how methods of observing the Universe have changed over time
-Naked eye
-Refracting telescope
-Reflecting telescope
-Technological advances allowed other parts of EM spectrum to be measured
7.19P
Why are some telescopes located outside the earth’s atmosphere?
-Atmosphere absorbs some λ of light e.g. x-rays, gamma rays
-Can’t be detected from Earth
-Allows to capture broader range of light
