Solar System Physics Flashcards
Why is it difficult to observe
evidence for a heliocentric model of the solar system?
Stellar parallax is not observed with the naked
eye because the stars are too far away and the Earth is orbiting too slowly about the Sun for other physical effects such as the Doppler shift of starlight to be easily measured
What was some of the first evidence against the geocentric model of the solar system?
Retrograde motion of Mars and Galileo’s observations of the phases of Venus using his invention of the telescope
What are the two groups of planets called?
Terrestrial and Jovian
Name all the Terrestrial planets
Mercury, Venus, Earth, Mars
Name all the Jovian planets
Jupiter, Saturn, Uranus, Neptune
What is 1 astronomical unit equal to?
The mean Earth-Sun distance (1.496 × 10¹¹) m
What are 3 types of non-planetary objects in the solar system?
Asteroids, comets and dwarf planets
What are asteroids and comets?
Small, irregular rocky bodies
What is the difference between an asteroid and a comet?
It’s location in the solar system
Where are asteroids found?
In the asteroid belt between the orbits of Mars and Jupiter
Where are comets found?
In the outer reaches of the solar system
What are The Kirkwood Gaps?
Regions in the asteroid belt where there are considerably fewer objects
What are The Kirkwood Gaps due to?
Orbital resonance effects due to the mass of Jupiter
What are Kuiper Belt objects?
All the astronomical ‘debris’ out beyond the orbit of Neptune
Give an example of Kuiper Belt objects
Dwarf planets such as Pluto and its largest moon Charon
Which equation is used to find the gravitational force between two point masses?
(F_12 ) ⃗=(Gm1 m2)/r^2 r ̂_12
In the gravitational force between two point masses equation, what does r ̂_12 represent?
A unit vector in the direction from m1 to m2
In the gravitational force between two point masses equation, what does G represent?
Newton’s gravitational constant
What is the magnitude of a body’s gravitational field represented by?
The gravitational force per unit mass
What can we also define the gravitational field as?
The gravitational acceleration, g
What led Einstein to his theory of relativity?
The equivalence of inertial mass and gravitational mass
What direction is the gravitational field at a planet’s surface directed?
Radially inwards and towards the planet’s centre
How can we calculate the acceleration due to gravity at that planet’s surface?
By equating Newton’s second law of motion to Newton’s law of gravitation
What is Newton’s second law of motion?
F=ma
What is Newton’s law of gravitation?
F=GMm/r²
What direction is surface gravity always assumed to be acting in?
Along a line joining the centres of mass of the two bodies under investigation
Do we usually have to state the direction of gravitational acceleration?
No, we are usually talking about the magnitude only
What is the surface gravity/gravitational acceleration for the Earth?
9.8 m/s²
What are the 2 consequences of the surface gravity equation (F=GM/r²)?
- Bodies accelerate as they fall
2. All bodies accelerate (fall) at the same rate, irrespective of their mass
What is the equation used to determine surface gravity?
F=GM/r²
What is the equation for density?
ρ=mass/volume
What is the formula for the volume of a sphere?
V=4/3xπR^3
How do we express a planet’s surface gravity in terms of its average density?
g=4/3xπGRρ
If two planets have the same average density, which planet will have the higher surface gravity?
The planet with the larger radius as it has more mass
If two planets have the same radius, which planet will have the higher surface gravity?
The denser planet
What is the proportionality between gravitational acceleration and average density?
They are in direct proportion to one another
What is escape velocity?
The minimum velocity needed for a projectile to escape the gravitational pull of a planet
How do we derive the formula for escape velocity?
Totalling up all forms of energy (kinetic and gravitational potential) and setting this equal to zero then rearranging to find v
What is the equation for kinetic energy?
Ek=1/2xmv²
What is the equation for gravitational potential energy?
Egp= GMm/R
Does escape velocity depend on the mass of the object escaping?
No
Where do high tides occur in the Earth’s oceans?
The sides nearest and farthest from the moon (moon’s gravity is strongest and weakest here)
Where do low tides occur on the Earth?
At the points on the Earth which lie at right angles to the points nearest and farthest from the moon
Why do low tides occur?
At those points on the Earth, the differential force is inward
What are spring tides?
Exceptionally high tides
When would spring tides occur?
When the Earth, the Moon and the Sun are all aligned
What are neap tides?
Exceptionally low tides
When would neap tides occur?
When the Moon and the Sun sit at right angles from the perspective of the Earth
How would you calculate the tidal force exerted on a satellite, S, in orbit around a planet between points A and C (centre of planet)?
The tidal force between points A and C, on the satellite due to the effect of the nearby planet is equal to the difference in the gravitational force at those points: FA − FC .
What is tidal force also known as?
Differential force
What is the equation for the tidal force between points A and C (centre of planet)?
FA-FC= 2GMmΔ/r^3
Where Δ is the distance from the satellite to the centre of the planet
