Physics- General Definitions.txt

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Physics- General Definitions.txt
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2013-05-05 01:23:07
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Physics IB
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General Definitions of IB Physics Terms.
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  1. Displacement
    Position of an object relative to its starting position.
  2. Velocity
    Rate of change of displacement.
  3. Speed
    Rate of change of distance.
  4. Acceleration
    • Rate of change of velocity.
    • Newton's First Law
    • An object continues in uniform motion in a straight line/ at rest unless a resultant force acts.
  5. Newton's Second Law
    The acceleration of an object is proportional to and in the same direction as its resultant force.
  6. Newton's Third Law
    When 2 objects react, the exert equal and opposite forces on each other.
  7. Linear Momentum
    The product of mass and velocity.
  8. Impulse
    Change in momentum.
  9. Law of conservation of momentum
    Momentum of object in system stays the same in a closed system.
  10. Work
    Force X distance moved in direction of force.
  11. Kinetic Energy
    The energy an object has due to it's motion
  12. Change in GPE
    • The energy an object has due to its position above the Earth
    • .
    • Elastic Collision
    • KE is conserved and objects bounce off with the same speed it did before in opposite directions.
  13. Inelastic Collision
    Maximum loss of KE, objects stick together & momentum is still conserved.
  14. Explosion
    Objects move away from each other, internal energy becomes KE.
  15. Efficiency
    Ratio of work out: energy put in.
  16. Mole
    Amount of substance that has the same number of molecules as the number of of molecules as the number of atoms in 12g of C-12.
  17. Molar Mass
    Mass of 1 mole of the substance.
  18. Avogadro's Constant
    Number of molecules in 1 mole = 6.022 × 10²³
  19. Specific Heat Capacity
    The energy needed to increase the temperature of of 1 kilo of an object by 1K.
  20. Thermal Capacity
    The energy needed to increase the temperature of an object by 1K.
  21. Specific Latent Heat
    Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.
  22. Pressure
    Force per unit area.
  23. Displacement (SHM)
    Distance away a particle is from its equilibrium position.
  24. Amplitude (SHM)
    Maximum displacement of a particle from its equilibrium position.
  25. Frequency (SHM)
    Number of oscillations produced per second.
  26. Period (SHM)
    Time taken for a complete oscillation.
  27. Phase Difference (SHM)
    The fraction of an oscillation that one wave moves behind another.
  28. Simple Harmonic Motion
    Motion where the acceleration of an object is proportional to & in the opposite direction to displacement. a = -ω2x
  29. Damping
    Process where the energy of an oscillating system decreases with amplitude by a dissipative force acting in the opposite direction.
  30. Natural frequency
    The frequency that a system naturally oscillates at.
  31. Forced oscillation
    An oscillation that occurs & stays , Where an object is forced to oscillate by an external force.
  32. Resonance
    When the frequency of a driving force matches the natural frequency of oscillation.
  33. Transverse wave
    Oscillations are at 90° to direction of energy transfer/ wave motion.
  34. Longitudinal wave
    Oscillations are parallel to direction of energy transfer/ wave motion.
  35. Crest
    Point on a wave with maximum positive displacement.
  36. Trough
    Point on a wave with maximum negative displacement.
  37. Compression
    Region (on a wave) where particles are closer together than they would be in their equilibrium state.
  38. Rarefaction
    Region (on a wave) where particles are further apart than they would be in their equilibrium state.
  39. Wavelength
    The shortest distance between 2 points on a wave that are in phase.
  40. Wave speed
    The speed at which wave fronts pass a stationary observer.
  41. Intensity
    The power per unit area received by an observer from a wave.
  42. Principle of superposition
    When 2 or more waves of the same type meet, the total displacement at a point on a wave is the displacements of the individual waves added at that point.
  43. Constructive/destructive interference
    Phase difference is 0/ out of phase& path difference is a whole 'n' of wavelength/ a fraction of it.
  44. Electric potential difference
    Work done per unit charge in moving a positive charge from one point in the (electric) field to another.
  45. Electronvolt
    The amount of energy an electron gains by moving through a potential difference of 1 volt.
  46. Electric current
    The rate of flow of electrical charge.
  47. Resistance
    The ratio of voltage across the material to the current flowing through it.
  48. Ohm's Law
    The current through a wire is proportional to the p.d. across it; as long as the temperature is constant.
  49. Electromotive force (emf)
    The power supplied by the supply per unit current.
  50. Internal resistance
    Resistance of a source (of power).
  51. Gravitational field strength
    The force per unit mass experienced by a small test mass placed in the field.
  52. Newton's universal law of gravitation
    Any point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to their separation².
  53. Electric field strength
    The force per unit charge experienced by a small test charge placed in the field.
  54. Magnetic field strength
    • F=BILsinø
    • Direction: 90° to field lines.
  55. Nuclide
    An atom with a particular nucleus configuration.
  56. Nucleon
    A proton or a neutron.
  57. Isotope
    An element with the same number of protons but a different number of neutrons.
  58. Radioactive half life
    The time taken for the total number of nuclei (of a radioactive substance) to halve.
  59. Unified atomic mass
    The mass of ½ of the nucleus of a C-12 isotope.
  60. Mass defect
    The difference in mass between a nucleus and its separate nucleons.
  61. Binding energy per nucleon
    The total binding energy for the nucleus divided by the total number of nucleons
  62. Binding energy
    The energy needed to break up a nucleus into its constituent nucleons.
  63. Degraded energy
    Energy transferred to surroundings that can no longer do useful work.
  64. Energy density
    The mean energy liberated per kg of a fuel.
  65. Fuel enrichment
    A process where you increase percentage of U-235 to make fission more likely.
  66. Moderator
    Slows down fast neutrons to increase the chance of more reactions. (So they don't pass through the nuclei)
  67. Control rod
    This absorbs neutrons to control chain reactions.
  68. Heat exchanger
    This allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. The thermal energy is transferred to heat water, and the steam that is produced turns the turbines.
  69. Photovoltaic cell
    Light hits semiconductors & electrons are released/ moved; creating an electric field.
  70. Solar heating panel
    Heat goes through glass pane & is absorbed by black pipes with running water in them.
  71. Albedo
    The ratio of reflected: incident radiation.
  72. Stefan- Boltzmann law
    Total power radiated ∝ T⁴ OR P= σAT⁴.
  73. Emissivity
    The ratio of power emitted by a body to the power emitted if it was a black body.
  74. Surface heat capacity
    The energy needed to raise the temperature of a unit area of a planet's surface by 1K.
  75. Enhanced greenhouse effect
    Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities
  76. Coefficient of volume expansion
    The fractional change in volume per degree change in temperature.
  77. Gravitational potential
    Work done per unit mass in bringing a test mass from infinity to that point in the field.
  78. Gravitational potential energy
    Work done in moving an object from infinity to that point.
  79. Electric potential
    The work done per unit charge in bringing a positive test charge from infinity to that point in the field.
  80. Electric potential energy
    The work done moving a charge from infinity to a point in an electric field.
  81. Isochoric
    Constant volume: no work is done.
  82. Isobaric
    Constant pressure: Work done is area under line.
  83. Isothermal
    Constant temperature: Work done= area under curve.
  84. Adiabatic
    No heat transfer: compression/ expansion. Work is done on/ by gas
  85. Standing waves
    Transfer no energy. They have the same amplitude and are in phase. Happens when a wave & its reflection interfere (or just 2 waves)
  86. One dimensional standing wave
    Happens when a wave reflects back from a boundary along the route it came.
  87. Doppler Effect
    The change in perceived frequency because the source or observer is moving.
  88. Rayleigh criterion
    2 points will be resolvable if the first minimum of the diffraction pattern of one source overlaps the central maximum of the diffraction pattern of the second source.
  89. Polarized light
    Light with waves that vibrate in 1 plane.
  90. Brewster's angle
    Happens when the transmitted ray is 90° to the reflected ray. The angle gives us the angle of incidence needed for plane-polarized light.
  91. Polariser
    A device that makes polarized light from an unpolarised beam.
  92. Analyser
    A polariser used to detect polarised light.
  93. Optically active substance
    A substance that rotates the plane of polarisation of light that goes through it.
  94. Stress analysis
    If polarised white light is shone on plastic, you can see the stress points where the coloured lines are.
  95. Magnetic flux
    A measure of the strength of a magnetic field over a given area/ number of field lines.
  96. Magnetic flux linkage
    The product of the magnetic flux and the number of turns in a given coil.
  97. Faraday's law
    The size of an induced emf is proportional to the rate of change of flux linkage.
  98. Lenz's law
    The direction of an induced current is such that it'll oppose the change causing it.
  99. de Broglie Hypothesis
    All particles have a wave like nature.
  100. Electron in a box model
    An electron has possible wavelengths like a standing wave on a string so electrons have discrete energies.
  101. Schrödinger's model
    This gives the probability of where the electron could be (probability regions called orbitals).
  102. Heisenberg uncertainty principle
    • You can only know 1 from each pair:
    • -momentum & position
    • -energy & time
  103. Decay constant
    Probability of decay of a nucleus per unit time
  104. Radioactive decay law
    The activity of a radioactive sample ∝ Number of radioactive nuclei present.
  105. Capacitance
    Charge per unit p.d. that can be stored on a capacitor.
  106. Quantum efficiency
    The ratio of the number of photoelectrons emitted: the number of photons incident on the pixel.
  107. Magnification
    The ratio of the length of the image on the CCD: the length of the object.
  108. Stellar cluster
    A group of stars that are physically near each other in space.
  109. Constellation
    A pattern of stars as seen from Earth that aren't physically near each other in space.
  110. Light year
    The distance that light travels in 1 year.
  111. Luminosity
    The total power emitted by a star.
  112. Apparent brightness
    The power received per unit area on Earth by a star.
  113. Cepheid
    A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.
  114. Red giant
    • -Red
    • -Comparatively cool
    • -Large
    • -Fuse elements other than Hydrogen
  115. Red Supergiant
    • -Red
    • -Large Mass
    • -Large Surface Area
    • -Large Luminosity
    • -Low Surface Temperature
  116. White Dwarfs
    • -Very Small/ Low Surface Area
    • -Large Surface Temperature
    • -White
  117. Visual Binary
    Stars can be distinguished using a telescope
  118. Spectroscopic Binary
    Analysis if its light spectrum shows 2 different classes of stars- the wavelengths show a periodic splitting in frequency.
  119. Eclipsing binary
    Analysis of the brightness of its light spectrum shows periodic dips. This is because on star is in the way of the other.
  120. Parsec
    A unit of distance that is equal to 3.26 light years
  121. Apparent magnitude
    How bright a star appears from Earth.
  122. Absolute magnitude
    The apparent magnitude a star would have if it was 10 parsecs away.
  123. Critical density
    The theoretical density of the universe that would create a flat universe.
  124. Hubble's Law
    The recessional velocity of a galaxy ∝ its distance away from Earth.
  125. Audible frequencies
    2Hz - 20KHz
  126. (Sound) Intensity
    Amount of energy that a sound wave brings to a unit area every second.
  127. (Sound) Intensity Level
    • 10 lg (I / I0);
    • where I0 = 1.0 × 10-12 Wm-2.
  128. Attenuation Coefficient
    The probability of a single photon being absorbed in 1 m of the material- use defining equation.
  129. Half-value thickness
    The half-value thickness is that thickness of material which will reduce the intensity of the (transmitted) beam by 50%
  130. Acoustic Impedance
    The product of of the density of a substance and the speed of sound in that substance.
  131. Exposure
    The total ionized charge produced in unit mass of air by a particular radiation. Q=mX.
  132. Absorbed Dose
    The energy absorbed per unit mass of tissue. E=mD.
  133. Quality Factor
    This allows doses of different types of radiation to be compared for their biological effects.
  134. Dose Equivalent
    The amount of energy absorbed
  135. Physical Half-Life
    • The time it takes for the activity of a sample
    • to halve.
  136. Biological Half-Life
    The time it takes the body to naturally eject half of an ingested sample of a radioactive isotope.

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