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Physics > Definitions > Flashcards

Definitions Flashcards

1
Q

Displacement

A

Position of an object relative to its starting position.

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2
Q

Velocity

A

Rate of change of displacement.

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3
Q

Speed

A

Rate of change of distance.

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4
Q

Acceleration

A

Rate of change of velocity.

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5
Q

Newton’s First Law

A

An object continues in uniform motion in a straight line/ at rest unless a resultant force acts.

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6
Q

Newton’s Second Law

A

The acceleration of an object is proportional to and in the same direction as its resultant force.

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7
Q

Newton’s Third Law

A

When 2 objects react, the exert equal and opposite forces on each other.

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8
Q

Linear Momentum

A

The product of mass and velocity.

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9
Q

Impulse

A

Change in momentum.

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10
Q

Law of conservation of momentum

A

Momentum of object in system stays the same in a closed system.

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11
Q

Work

A

Force X distance moved in direction of force.

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12
Q

Kinetic Energy

A

The energy an object has due to it’s motion

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13
Q

Change in GPE

A

The energy an object has due to its position above the Earth.

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14
Q

Elastic Collision

A

KE is conserved and objects bounce off with the same speed it did before in opposite directions.

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15
Q

Inelastic Collision

A

Maximum loss of KE, objects stick together & momentum is still conserved.

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16
Q

Explosion

A

Objects move away from each other, internal energy becomes KE.

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17
Q

Efficiency

A

Ratio of work out: energy put in.

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18
Q

Mole

A

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.

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19
Q

Molar Mass

A

Mass of 1 mole of the substance.

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20
Q

Avogadro’s Constant

A

Number of molecules in 1 mole = 6.022 × 10²³

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21
Q

Specific Heat Capacity

A

The energy needed to increase the temperature of of 1 kilo of an object by 1K.

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22
Q

Thermal Capacity

A

The energy needed to increase the temperature of an object by 1K.

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23
Q

Specific Latent Heat

A

Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.

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24
Q

Pressure

A

Force per unit area.

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25
Q

Displacement (SHM)

A

Distance away a particle is from its equilibrium position.

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26
Q

Amplitude (SHM)

A

Maximum displacement of a particle from its equilibrium position.

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27
Q

Frequency (SHM)

A

Number of oscillations produced per second.

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28
Q

Period (SHM)

A

Time taken for a complete oscillation.

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29
Q

Phase Difference (SHM)

A

The fraction of an oscillation that one wave moves behind another.

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30
Q

Simple Harmonic Motion

A

Motion where the acceleration of an object is proportional to & in the opposite direction to displacement. a = -ω2x

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31
Q

Damping

A

Process where the energy of an oscillating system decreases with amplitude by a dissipative force acting in the opposite direction.

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32
Q

Natural frequency

A

The frequency that a system naturally oscillates at.

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33
Q

Forced oscillation

A

An oscillation that occurs & stays , Where an object is forced to oscillate by an external force.

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34
Q

Resonance

A

When the frequency of a driving force matches the natural frequency of oscillation.

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35
Q

Transverse wave

A

Oscillations are at 90° to direction of energy transfer/ wave motion.

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36
Q

Longitudinal wave

A

Oscillations are parallel to direction of energy transfer/ wave motion.

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37
Q

Crest

A

Point on a wave with maximum positive displacement.

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38
Q

Trough

A

Point on a wave with maximum negative displacement.

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39
Q

Compression

A

Region (on a wave) where particles are closer together than they would be in their equilibrium state.

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40
Q

Rarefaction

A

Region (on a wave) where particles are further apart than they would be in their equilibrium state.

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41
Q

Wavelength

A

The shortest distance between 2 points on a wave that are in phase.

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42
Q

Wave speed

A

The speed at which wave fronts pass a stationary observer.

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43
Q

Intensity

A

The power per unit area received by an observer from a wave.

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44
Q

Principle of superposition

A

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.

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45
Q

Constructive/destructive interference

A

Phase difference is 0/ out of phase& path difference is a whole ‘n’ of wavelength/ a fraction of it.

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46
Q

Electric potential difference

A

Work done per unit charge in moving a positive charge from one point in the (electric) field to another.

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47
Q

Electronvolt

A

The amount of energy an electron gains by moving through a potential difference of 1 volt.

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48
Q

Electric current

A

The rate of flow of electrical charge.

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49
Q

Resistance

A

The ratio of voltage across the material to the current flowing through it.

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50
Q

Ohm’s Law

A

The current through a wire is proportional to the p.d. across it; as long as the temperature is constant.

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51
Q

Electromotive force (emf)

A

The power supplied by the supply per unit current.

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52
Q

Internal resistance

A

Resistance if a source (of power).

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53
Q

Gravitational field strength

A

The force per unit mass experienced by a small test mass placed in the field.

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54
Q

Newton’s universal law of gravitation

A

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.

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55
Q

Electric field strength

A

The force per unit charge experienced by a small test charge placed in the field.

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56
Q

Magnetic field strength

A

F=BILsinø

Direction: 90° to field lines.

57
Q

Nuclide

A

An atom with a particular nucleus configuration.

58
Q

Nucleon

A

A proton or a neutron.

59
Q

Isotope

A

An element with the same number of protons but a different number of neutrons.

60
Q

Radioactive half life

A

The time taken for the total number of nuclei (of a radioactive substance) to halve.

61
Q

Unified atomic mass

A

The mass of ½ of the nucleus of a C-12 isotope.

62
Q

Mass defect

A

The difference in mass between a nucleus and its separate nucleons.

63
Q

Binding energy per nucleon

A

The total binding energy for the nucleus divided by the total number of nucleons

64
Q

Binding energy

A

The energy needed to break up a nucleus into its constituent nucleons.

65
Q

Degraded energy

A

Energy transferred to surroundings that can no longer do useful work.

66
Q

Energy density

A

The mean energy liberated per kg of a fuel.

67
Q

Fuel enrichment

A

A process where you increase percentage of U-235 to make fission more likely.

68
Q

Moderator

A

Slows down fast neutrons to increase the chance of more reactions. (So they don’t pass through the nuclei)

69
Q

Control rod

A

This absorbs neutrons to control chain reactions.

70
Q

Heat exchanger

A

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.

71
Q

Photovoltaic cell

A

Light hits semiconductors & electrons are released/ moved; creating an electric field.

72
Q

Solar heating panel

A

Heat goes through glass pane & is absorbed by black pipes with running water in them.

73
Q

Albedo

A

The ratio of reflected: incident radiation.

74
Q

Stefan- Boltzmann law

A

Total power radiated ∝ T⁴ OR P= σAT⁴.

75
Q

Emissivity

A

The ratio of power emitted by a body to the power emitted if it was a black body.

76
Q

Surface heat capacity

A

The energy needed to raise the temperature of a unit area of a planet’s surface by 1K.

77
Q

Enhanced greenhouse effect

A

Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities

78
Q

Coefficient of volume expansion

A

The fractional change in volume per degree change in temperature.

79
Q

Gravitational potential

A

Work done per unit mass in bringing a test mass from infinity to that point in the field.

80
Q

*Gravitational potential energy

A

Work done in moving an object from infinity to that point.

81
Q

Electric potential

A

The work done per unit charge in bringing a positive test charge from infinity to that point in the field.

82
Q

Electric potential energy

A

The work done moving a charge from infinity to a point in an electric field.

83
Q

Isochoric

A

Constant volume: no work is done.

84
Q

Isobaric

A

Constant pressure: Work done is area under line.

85
Q

Isothermal

A

Constant temperature: Work done= area under curve.

86
Q

Adiabatic

A

No heat transfer: compression/ expansion. Work is done on/ by gas

87
Q

Standing waves

A

Transfer no energy. They have the same amplitude and are in phase. Happens when a wave & its reflection interfere (or just 2 waves)

88
Q

One dimensional standing wave

A

Happens when a wave reflects back from a boundary along the route it came.

89
Q

Doppler Effect

A

The change in perceived frequency because the source or observer is moving.

90
Q

Rayleigh criterion

A

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.

91
Q

Polarized light

A

Light with waves that vibrate in 1 plane.

92
Q

Brewster’s angle

A

Happens when the transmitted ray is 90° to the reflected ray. The angle gives us the angle of incidence needed for plane-polarized light.

93
Q

Polariser

A

A device that makes polarized light from an unpolarised beam.

94
Q

Analyser

A

A polariser used to detect polarised light.

95
Q

Optically active substance

A

A substance that rotates the plane of polarisation of light that goes through it.

96
Q

Stress analysis

A

If polarised white light is shone on plastic, you can see the stress points where the coloured lines are.

97
Q

Magnetic flux

A

A measure of the strength of a magnetic field over a given area/ number of field lines.

98
Q

Magnetic flux linkage

A

The product of the magnetic flux and the number of turns in a given coil.

99
Q

Faraday’s law

A

The size of an induced emf is proportional to the rate of change of flux linkage.

100
Q

Lenz’s law

A

The direction of an induced current is such that it’ll oppose the change causing it.

101
Q

de Broglie Hypothesis

A

All particles have a wave like nature.

102
Q

Electron in a box model

A

An electron has possible wavelengths like a standing wave on a string so electrons have discrete energies.

103
Q

Schrödinger’s model

A

This gives the probability of where the electron could be (probability regions called orbitals).

104
Q

Heisenberg uncertainty principle

A

You can only know 1 from each pair:

  • momentum & position
  • energy & time
105
Q

Decay constant

A

Probability of decay of a nucleus per unit time

106
Q

Radioactive decay law

A

The activity of a radioactive sample ∝ Number of radioactive nuclei present.

107
Q

Capacitance

A

Charge per unit p.d. that can be stored on a capacitor.

108
Q

Quantum efficiency

A

The ratio of the number of photoelectrons emitted: the number of photons incident on the pixel.

109
Q

Magnification

A

The ratio of the length of the image on the CCD: the length of the object.

110
Q

Stellar cluster

A

A group of stars that are physically near each other in space.

111
Q

Constellation

A

A pattern of stars as seen from Earth that aren’t physically near each other in space.

112
Q

Light year

A

The distance that light travels in 1 year.

113
Q

Luminosity

A

The total power emitted by a star.

114
Q

Apparent brightness

A

The power received per unit area on Earth by a star.

115
Q

Cepheid

A

A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.

116
Q

Red giant

A
  • Red
  • Comparatively cool
  • Large
  • Fuse elements other than Hydrogen
117
Q

Red Supergiant

A
  • Red
  • Large Mass
  • Large Surface Area
  • Large Luminosity
  • Low Surface Temperature
118
Q

White Dwarfs

A

Very Small/ Low Surface Area

  • Large Surface Temperature
  • White
119
Q

Visual Binary

A

Stars can be distinguished using a telescope

120
Q

Spectroscopic Binary

A

Analysis if its light spectrum shows 2 different classes of stars- the wavelengths show a periodic splitting in frequency.

121
Q

Eclipsing binary

A

Analysis of the brightness of its light spectrum shows periodic dips. This is because on star is in the way of the other.

122
Q

Parsec

A

A unit of distance that is equal to 3.26 light years

123
Q

Apparent magnitude

A

How bright a star appears from Earth.

124
Q

Absolute magnitude

A

The apparent magnitude a star would have if it was 10 parsecs away.

125
Q

Critical density

A

The theoretical density of the universe that would create a flat universe.

126
Q

Hubble’s Law

A

The recessional velocity of a galaxy ∝ its distance away from Earth.

127
Q

Audible frequencies

A

2Hz - 20KHz

128
Q

(Sound) Intensity

A

Amount of energy that a sound wave brings to a unit area every second.

129
Q

(Sound) Intensity Level

A 
10 lg (I / I0);
where I0 = 1.0 × 10-12 Wm-2.
130
Q

Attenuation Coefficient

A

The probability of a single photon being absorbed in 1 m of the material- use defining equation.

131
Q

Half-value thickness

A

The half-value thickness is that thickness of material which will reduce the intensity of the (transmitted) beam by 50%

132
Q

Acoustic Impedance

A

The product of of the density of a substance and the speed of sound in that substance.

133
Q

Exposure

A

The total ionized charge produced in unit mass of air by a particular radiation. Q=mX.

134
Q

Absorbed Dose

A

The energy absorbed per unit mass of tissue. E=mD.

135
Q

Quality Factor

A

This allows doses of different types of radiation to be compared for their biological effects.

136
Q

Dose Equivalent

A

The amount of energy absorbed

137
Q

Physical Half-Life

A

The time it takes for the activity of a sample

to halve.

138
Q

Biological Half-Life

A

The time it takes the body to naturally eject half of an ingested sample of a radioactive isotope.

Physics (1 decks)

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