Studied by 17 people
Solar System
A collection of bodies that are gravitationally bound to the sun (planets
Galaxy
A collection of billions of stars
Galactic Cluster
A collection of galaxies held together by gravity
Stellar Cluster
A collection of stars held together by gravity
Constellation
A collection of stars which are not necessarily close together, and form a recognisable group
Single Star
A star not gravitationally bound by another
Astronomical Unit
The mean earth-sun distance
Light Year
The distance light travels in a year
Stellar Parallax
The apparent movement of a nearby object against the background as seen from two positions
Parallax Angle
The difference in angular positions
Luminosity
The total power output of a star (amount of energy radiated by a star per second)
Apparent Brightness
The power output per unit area at a given distance
Black Body
A perfect absorber and emitter of radiation
Wien's Law
The wavelength at peak intensity for a black body is inversely proportional to the surface temperature
Cepheid Variable
A star that varies in brightness over a period of days
Chandrasekhar Limit
Mass < 1.4M
Oppenheimer-Volkof Limit
Mass > 2.5M
Hubble's Law
There is a linear relationship between the recessional velocity of a galaxy and its distance
Critical Density
The density that will stop the expansion of the universe (value where universe will contract)
Cosmic Scale Factor 'R'
The relative expansion rate of the universe
Binding energy
The energy needed to completely separate a nucleus into its nucleons
Model of atom based on Rutherford's experiment
Most of the mass of an atom is confined within a very small volume/nucleus
All the positive charge is confined within a very small volume/nucleus
Electrons orbit the nucleus in circular orbits
Systematic error
An error that is identical for each reading
Random error
Measurements are above and below the true value with equal probability
Directly proportional
A graph of 2 directly proportional quantities will be a straight line through the oirign
Linear
Produces a straight line graph
Inversely proportional
Y is proportional to 1/x or yx=constant
Precise
A high number of significant figures with a small spread of results
Accurate
Near true value
Vector
Quantity with magnitude and direction
Scalar
Quantity with magnitude only
Displacement
The distance moved in a stated direction (distance and direction from starting point)
Speed
Rate of change of distance (per unit time)
Velocity
Rate of change of displacement
Acceleration
Rate of change of velocity
Instantaneous speed/velocity
Change in distance/displacement divided by one particular instant of time
Average speed/velocity
Change in distance/displacement divided by time taken over a period of time
Trajectory
Shape of the path that a moving object makes in the air
Newton's 1st law
An object continues in uniform motion or a straight line, or at rest, unless a resultant external force acts on it
Newton's 2nd law
Force = mass x acceleration
Newton's 3rd law
If body A exerts Body B, then body B exerts an equal and opposite force on Body A
Equilibrium
No resultant force in any direction (translational); No resultant momentum at any point (rotational)
Linear momentum
Mass x velocity
Impulse
Force x time or change in momentum
Law of conservation of linear momentum
In an isolated system, momentum is constant
Work
Force x distance moved in direction of force
Kinetic energy
The energy a body possesses by virtue of its motion
Principle of conservation of energy
Energy cannot be created or destroyed, only transformed from one form to another
Inelastic collision
When there is a change in kinetic energy
Elastic collision
When there is no change in kinetic energy
Power
Rate at which energy is transferred (or rate at which work is done)
Efficiency
Ratio of useful energy to energy transferred
Temperature
A property that determines the direction of heat flow from two bodies in thermal contact. It measures average random kinetic energy of particles of a substance
Temperature in Kelvin
Celsius + 273
Kelvin (absolute temperature)
Proportional to average kinetic energy of particles
Thermal energy
Energy that is transferred by a temperature difference
Internal energy
Total potential energy + random kinetic energy in a substance
Thermal capacity
Amount of energy needed to raise temperature of object by 1 kelvin
Specific heat capacity
Amount of thermal energy needed to raise temperature of unit mass of a substance by 1 kelvin
Specific latent heat
Amount of thermal energy needed to change the state of unit mass of a substance at constant temperature
Mole
Amount of substance that contains same number of units that are in 12g of carbon-12 (6.022*10^23)
Molar mass
Mass of one mole of a substance
Avogadro's constant
Number of atoms in 0.012 kg of Carbon 12 (6*10^23)
Pressure
Normal force to an area per unit area
Ideal gas assumptions
Gas consists of a large number of molecules; molecules move with a range of speeds; the volume of the molecules is negligible compared with the volume of gas itself; the collisions of the molecules with each other and the container are elastic; molecules exert no forces on each other or the container except when in contact; the duration of collisions is very small compared with the time between collisions; the molecules obey Newton's laws
Rays
Show direction of energy transfer of a wave
Wave fronts
Highlight the part of a wave that is moving together (in phase)
Displacement (waves)
Distance any point on a wave has moved from it's undisturbed position
Amplitude
Maximum displacement from mean position
Period
Time taken for one complete oscillation
Frequency
Number of oscillations that take place per unit time
Wavelength
Shortest distance along a wave between the points that are in phase
Phase difference
Time difference by which one wave leads or lags another
Wave speed
Speed at which wave fronts pass a stationary observer
Intensity
Average amount of energy transported by a wave in the direction of wave propagation, per unit area per unit time
Principle of superposition
When 2 or more waves meet, the resultant displacement is the sum of individual displacements
Simple harmonic motion
Periodic motion in which the restoring force/acceleration is proportional to the displacement and in the opposite direction
Longitudinal wave
Oscillations parallel to direction of energy transfer
Transverse wave
Oscillations are perpendicular to direction of energy transfer
Polarised light
Light in which electric field vector vibrates in one place only
Electric potential difference
Between 2 points, is work done per unit charge to move a small positive charge between two points
Electric current
Rate of flow of electrical charge
Electromotive force (EMF)
Total energy difference per unit charge around the circuit (PD When no current flows in a circuit)
Electronvolt
Energy gained by an electron when moving through potential difference of one volt
Resistance
Ratio between potential difference across component/circuit and current through it
Ohm's law
When temperature is constant, the current through metallic conductor is proportional to potential difference across it
Volt
1 joule per coulomb
Electric field strength
Force per unit charge on a small positive test charge
Drift speed
Average speed attained by a particle due to an electric field
Kirchoff's laws
Current flowing towards a junction = total current flowing away from junction
Sum of EMF in any closed loop = sum of potential drops in the loop
Newton's Universal Law of Gravitation
Gravitational force between 2 point masses is proportional to the product of 2 masses and inversely proportional to their distance squared
Gravitational field strength
Force exerted per unit mass on small point mass at a location
Fuel
Source of energy in usable form
Stefan boltzmann law
Power per unit area emitted by a body is proportional to the absolute temperature ^4
Energy density
Energy obtained from unit volume
Specific energy
Energy obtained from unit mass
Emissivity
Ratio of energy emitted (per unit area) of a body to energy emitted by a black body of same dimensions at same temperature
Surface heat capacity
Energy required to increase temperature of 1 m^2 of surface by 1 kelvin
Critical mass
Minimum mass needed to sustain fission
Nucleon
Particle in the nucleus of an atom (proton or neutron)
Note 
Flashcard (77)