Newtonian World and Astrophysics Flashcards
1
Q
What are gravitational fields
A
A field created around any object with mass, extending all the way to infinity, but diminishing as the distance from the centre of mass of the object increases.
2
Q
Gravitational field strength equation
A
g=F
m
3
Q
Newton’s law of gravitation for the force between two point masses
A
F=- GMm
r^2
4
Q
What is the value of G (gravitational constant)
A
6.67x10^-11
5
Q
Gravitational field strength equation for a point mass
A
g=-GM
r^2
6
Q
Kepler’s 1st Law of motion
A
The orbit of a planet is an ellipse with the Sun at one of the two foci
7
Q
Keplers 2nd Law of planetary motion
A
A line segment connecting a planet to the sun sweeps out equal areas during equal intervals of time
8
Q
Keplers 3rd Law of planetary motion
A
The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the sun
9
Q
Aphelion
A
The furthest point from the Sun in an orbit
10
Q
Perihelion
A
The closest point to the Sun in an orbit
11
Q
Eccentricity
A
A measure of the elongation of an ellipse
12
Q
Ellipse
A
An elongated ‘circle’ with two foci
13
Q
What is the AU astronomical unit
A
This is the mean distance from the earth to the sun 1.50x10^11
14
Q
Orbital Period equation
A
T^2= (4π^2) r^3
GM
15
Q
What is a geostationary orbit
A
This is the orbit a geostationary satellite has and it remains in the same position relative to a spot on the earths surface, by orbiting in the direction of the Earth’s rotation over the equator with a period of 24 hours.
16
Q
Uses of geostationary satellites
A
Communications, military, gps (global positioning system), weather and climate, scientific research
17
Q
What is gravitational potential at a point
A
This is the work done in bringing unit mass from infinity to the point and it is zero at infinity
18
Q
What is gravitational potential energy
A
This is the capacity for doing work as a result of an object’s position in a gravitational field
19
Q
What is escape velocity
A
This is the minimum velocity at which an object has just enough energy to leave a specified gravitational field
20
Q
Gravitational potential energy equation
A
Vg = -GM and Vg is directly proportional to 1/r
r
21
Q
Gravitational potential energy equation
A
E= mVg = -GMm
r
22
Q
What is the area under a force distance graph
A
Work done
23
Q
What is the universe
A
This is everything that exists within space and time
24
Q
Galaxy
A
This is a collection of stars and interstellar dust and gas bound together by their mutual gravitational force
25
Solar System
This is a planetary system consisting of a star and at least one planet in orbit around it
26
Planet
This is an object in orbit around a star with a mass large enough for its own gravity to give it a round shape that undergoes no fusion reactions and that has cleared its orbit of most other objects
27
Comet
This is a small irregular body made of ice, dust and small pieces of rock in an (often highly eccentric elliptical) orbit around the sun- as they approach the sun, some comets develop spectacular tails
28
Planetary Satellite
This is a body in orbit around a planet- it may be natural or artificial
29
Asteroid
This is a small rocky airless object that orbits the sun
30
Dwarf Planet
This is a celestial body that orbits the sun , has enough mass to assume a nearly round shape but it has not cleared its orbit of other objects
31
What is the Cosmological principle
This is the assumption that when viewed on a large enough scale, the Universe is homogenous (density is same everywhere) and isotopic (its the same in all directions), and the laws of physics are universal
32
What is nebula
This is a cloud of dust and gas (mainly hydrogen), often many hundreds of times larger than our solar system
33
Astronomical Unit (AU)
This is the average distance from the earth to the sun 1.50x10^11m
34
Light-Year (ly)
This is the distance travelled by light in a vacuum in a time of one year, 9.46x10^16m
35
The parsec (pc)
This is the distance at which a radius of one AU subtends an angle of one arc second 3.09x10^16m
36
Distance of a nearby star
1
Parallax angle (arc seconds)
37
What is a white dwarf
A very dense star formed from the core of a red giant, in which no fusion occurs
38
What is a red giant
This is an expanding star at the end of its life, with an inert core in which fusion no longer takes place but does in the shell around the core with lighter elements
39
What is electron degeneracy pressure
This is created by electrons in the core of a collapsing star due to the fact 2 electrons cannot exist in the same energy state (Pauli exclusion).
40
What is Chandrasekhar limit
This is the mass of a star's core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse, 1.44 solar masses
41
Characteristics of a neutron star
This is formed if the mass of the core is greater than 1.44 Ms as the gravitational collapse continues. Almost entirely made up of neutrons and can be very small
42
Characteristics of a black hole
The remnant core of a massive star after it has gone supernova and the core has collapsed so far that in order to escape it, an object would need a velocity greater than the speed of light and therefore nothing can escape. Vary in mass
43
Emission line spectra
each element produces a unique emission line spectrum because of its unique set of energy levels
44
Continuous spectra
All visible frequencies or wavelengths are present. The atoms of a heated solid metal will produce this type of spectrum
45
Absorption line spectra
This type of spectrum has series of dark spectral lines against the background of a continuous spectrum. The dark lines have exactly the same wavelengths as the bright emission spectra lines for the same gas atoms
46
What is a diffraction grating
This is an optimal component with regularly spaced slits or lines that diffract and split light into beams or different colour travelling in different directions
47
Equation for spectra
dsinθ =n λ
48
Stefan's law
This states that the total power radiated per unit surface area of a black body is directly proportional to the fourth power of the absolute temperature of the black body.
49
Excited definition
This means containing an electron or electrons that have absorbed energy and have been boosted into a higher energy level
50
Red supergiant
This is a huge star in the last stages of its life before it 'explodes' in a supernova.
51
What is luminosity
This is the total radiant power output of a star
52
Black body
This is an idealised object that absorbs all the electromagnetic radiation incident on it and when in thermal equilibrium, emits a distribution of wavelengths at a specific temperature
53
Kinetic theory of gases model definition and its assumptions
This is a model used to describe the behaviour of the atoms or molecules in an ideal gas. Assumptions: large number of molecules in random, rapid motion. Particles occupy negligible volume compared to volume of gas. There are negligible forces between particles except during collisions. All collisions are perfectly elastic and the time of the collisions is negligible compared to the time between the collisions.
54
Pressure in terms of Newtonian theory
3rd law shows that the total pressure on the wall is equal to the sum of the force of each collision between atoms in the gas and the wall, and it's area for a container
55
Number of particles N=
n x Na
(Number of moles) x Avogadro's constant (6.02x1023)
56
The molar mass definition
Mass of one mole of the substance
57
Mass of a sample =
Number of moles x Molar Mass
m= n x M
58
Boyle's law
For a fixed mass of gas at constant temperature p is inversely proportional to V. pV is a constant
59
What is oscillating motion
Oscillating motion is repetitive motion of an object around its equilibrium position
60
Simple harmonic motion
Oscillating motion for which the acceleration of the object is directly proportional to its displacement and is directed towards some fixed point
61
Isochronous oscillator
This has the same period regardless of amplitude. The period of an isochronous oscillator is independent of its amplitude.
62
Displacement
The distance from equilibrium position
63
Amplitude
The maximum displacement from the equilibrium position
64
Period
The time taken to complete one full oscillation
65
Frequency
The number of complete oscillations per unit time
66
Phase difference
The difference in displacement between two oscillating objects or the displacement of an oscillating object at different times
67
Damping
This is the process by which the amplitude of the oscillations decreases over time when an external force acts on it
68
Light damping and example
Occurs naturally and the amplitude decreases exponentially with the period almost unchanged
69
Heavy damping and example
Period increases and the amplitude decreases dramatically. Pendulum oscillating in water
70
Critical or very heavy damping and example
The object stops before one oscillation is completed. Pendulum oscillating in treacle
71
Free oscillation
The motion of a mechanical system displaced from its equilibrium position and then allowed to oscillate without any external factors
72
Forced oscillation
An oscillation in which a periodic driver force is applied to an oscillator
73
Driving frequency
The frequency with which the periodic driver force is applied to a system in forced oscillation
74
Natural frequency
The frequency of a free oscillation
75
Resonance
The increase in amplitude of a forced oscillation when the driving frequency matches the natural frequency of the oscillating system. If not damped the system may break.
76
Practical example of a forced oscillation
Suspension systems in cars and bikes absorbing the energy from bumps
77
Practical example of resonance
Many musical instruments resonate to produce louder notes. Microwaves cause water molecules to resonate. Tuning circuits in radios use resonance effects to select the correct frequency radio wave signal .
78
Triple point
For a given substance, one specific temperature and pressure at which all three phases (solid,liquid and gas) of that substance can exist in thermodynamic equilibrium
79
Temperature in kelvin
Temperature in degrees + 273
80
Absolute zero
The lowest possible temperature, the temperature at which substances have minimum internal energy
81
Thermal equilibrium
A state in which there is no net flow of thermal energy between the objects involved. Objects in thermal equilibrium must be at the same temperature.
82
Kinetic model
The kinetic model describes all substances as made of atoms, ions or molecules, arranged differently depending on the phase of the substance
83
Brownian motion
This is the continuous random motion of small particles suspended in a fluid
84
Solids
Fixed volume, fixed shape, strong electrostatic forces of attraction between particles, low kinetic energy, high density, negligible compressibility, arranged in a regular 3-dimensional structure packed closely together, can vibrate but cannot move out of their positions in the structure
85
Liquids
Fixed volume, not fixed shape, intermediate kinetic energy, low density, very low compressibility, weak electrostatic forces of attraction between the particles, particles free to move around but still very close together, this flows easily and can change position
86
Gases
Volume not fixed, shape not fixed, high kinetic energy, very low density, high compressibility, negligible electrostatic forces between particles almost none, particles free to move around and far apart from each other, they move quickly in straight lines colliding with the walls of the container and each other
87
Internal energy
The internal energy of a substance is defined as the sum of the random distribution of kinetic and potential energies associated with the molecules of a system
88
Specific heat capacity
The specific heat capacity of a substance is defined as the energy required per unit mass to change the temperature by 1 kelvin or degrees Celsius
89
Specific latent heat
This specific latent heat of a substance is defined as the energy required to change the phase per unit mass while at a constant temperature
90
Specific latent heat of fusion Lf
When the substance changes from solid to liquid phase
91
Specific latent heat of vaporisation
When the substance changes from liquid to gas
92
Absolute scale of temperature
A scale for measuring temperature based on absolute zero and the triple point of pure water
93
Doppler effect
This is the change in the frequency and wavelength of waves received from an object moving relative to an observer compared with what would be observed without relative motion.
94
Hubble's law
The recessional speed of a galaxy is almost directly proportional to its distance from the earth
95
Big Bang Theory
This is the theory that at a moment in the past all the matter in the Universe was contained in a singularity, the beginning of space and time, that expanded rapidly outwards. The region was much hotter and denser that it is today.
96
Blue shift
The shortening of observed wavelength that occurs when a wave source is moving towards the observer- in astronomy, if a galaxy is moving towards the earth, the absorption lines in its spectrum will be blue shifted, that is, moved towards the blue end of the spectrum.
97
Red shift
The lengthening of observed wavelength that occurs when an object is moving away from the observer - in astronomy, if a galaxy is moving away from the earth (receding), the absorption lines in its spectrum will be red-shifted
98
Stellar parallax
A technique used to determine the distance to stars that are relatively close to the earth (less than 100pc) by comparing their apparent positions against distant stars at time 6 months apart
99
Planetary nebula
The outer layers of a red giant that have drifted off into space, leaving the hot core behind at the centre as a white dwarf
100
Wien's displacement law
The peak wavelength λmax at which the intensity of radiation from a black body is a maximum is inversely proportional to the absolute temperature T of the black body
101
Hubble constant Ho
The gradient of a line of best fit for a plot of recessional speed against distance from Earth of other galaxies
102
Estimation for the age of the universe
t is proportional to Ho^-1
103
Current ideas of the universe
Universe is made up of dark energy, dark matter and a small percentage of ordinary matter
104
Evolution of the universe after the Big Bang to the present
Time and space are created. The universe is a singularity- it is infinitely dense and hot.
