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A level physics formulas > Definitions > Flashcards

Definitions Flashcards

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1
Q

Random Error

A

when the
measured readings are

scattered about the true reading

with no fixed pattern

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2
Q

Systematic Error

A

when the
measured readings are

consistently larger
or consistently smaller

than the true reading

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3
Q

Accuracy

A

how close the measured reading is
to the true value

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4
Q

Precision of a set of readings

A

how close the measured readings are
to each other

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5
Q

Precision of an instrument

A

the size of the smallest division

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6
Q

scalar quantity

A

a physical quantity that has magnitude only

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7
Q

vector quantity

A

a physical quantity that has both magnitude and direction

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8
Q

Displacement

A

[magnitude] minimum straight line distance between start and endpoints

[direction] in that direction

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9
Q

Distance

A

length of actual path followed

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10
Q

Velocity

A

rate of change of displacement

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11
Q

Speed

A

rate of change of distance

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12
Q

Acceleration

A

rate of change of velocity

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13
Q

[TESTED]** Newton’s First Law of Motion **[2020]

A

Newton’s First Law of Motion states that

an object continues at rest or
with constant velocity

unless acted upon by an external resultant force

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14
Q

Newton’s Second Law of Motion

A

Newton’s Second Law of Motion states that

the rate of change of momentum of a body is

[magnitude] directly proportional to the resultant force acting on it

[direction] and in the direction of the resultant force

Fnet α dp/dt

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15
Q

Newton’s Third Law of Motion

A

Newton’s Third Law of Motion states that

when body A exerts a force on body B, body B exerts on body A a force of

the same type that is

equal in magnitude and

opposite in direction.

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16
Q

Mass of a body

A

property of a body which resists change in motion

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17
Q

Weight of a body

A

force acting on the body due to a gravitational field

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18
Q

Linear Momentum

A

product of its mass and velocity

p = mv

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19
Q

Force

A

rate of change of momentum

F = dp/dt

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20
Q

Impulse

A

product of resultant force and
time duration of impact

∆p = Fnet ∆t

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21
Q

The Principle of Conservation of Linear Momentum

A

The Principle of Conservation of Linear Momentum states that

the total linear momentum of an

isolated system of interacting bodies

before and after collision remains constant

if no net external force acts on the system

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22
Q

Perfectly elastic collisions (distinguishing property)

A

total kinetic energy of the system of bodies

before and after collision remains the same

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23
Q

[TESTED]** Inelastic collisions (distinguishing property) **[2020]

A

total kinetic energy of system of bodies

after collision is less than before

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24
Q

[TESTED]** Perfectly inelastic collisions (distinguishing property) **[2020]

A

masses stick together and

move off with same velocity after collision

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25
Q

[TESTED]** Field of a Force **[2020]

A

a region of space in which a force acts on a particle

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26
Q

Centre of Gravity

A

the single point where

the weight of a body may be considered to act

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27
Q

Moment of a Force

A

he product of the force and the

perpendicular distance to the pivot

from the line of action

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28
Q

Couple

A

a pair of forces that are

equal in magnitude and

opposite in direction

that does not act along the same line of action

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29
Q

Torque of a Couple

A

product of one of a pair forces and

the perpendicular distance between the forces

torque = F x d

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30
Q

Translational Equilibrium

A

[magnitude] no resultant force

[direction] in any direction
Rotational Equilibrium ———————————————- [magnitude] no resultant torque

[direction] about any point

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31
Q

Equilibrium

A

when there is no resultant force in any direction and

there is no resultant torque about any point

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32
Q

Principle of Moments

A

The principle of moments states that

for a body in rotational equilibrium,

sum of clockwise moments

about any point is equal to

sum of anti-clockwise moments

about the same point

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33
Q

Hooke’s Law

A

Hooke’s Law states that

the change in length of a material is directly proportional to

the force applied on it

when the limit of proportionality is not exceeded.

F = kx

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34
Q

Pressure

A

force acting normally

per unit area of a surface

p = F/A

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35
Q

Upthrust

A

a force

equal in magnitude and

opposite in direction to the

weight of fluid displaced by submerged or floating object

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36
Q

Tension

A

a force

along the length of a body

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37
Q

Friction

A

a force

that opposes relative motion between surfaces in contact.

It can also act to oppose
impending relative motion of surfaces.

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38
Q

Normal Contact Force

A

a force

exerted perpendicular to surfaces

that are physically touching

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39
Q

Viscous Force

A

a dissipative force that

acts when there is relative motion

between a body and the fluid (either a gas or liquid) surrounding the body.

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40
Q

Lift

A

a force

which acts perpendicular to the

direction of relative flow of surrounding fluid

when there is relative motion

between body and fluid

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41
Q

Work Done

A

the product of the force and

the displacement in the direction of the force

W = Fscosθ

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42
Q

(Translational) Kinetic Energy

A

the ability of a mass
to do work

due to its speed

Ek = 1/2 mv²

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43
Q

[TESTED]** Gravitational Potential Energy **[2020]

A

the ability of a mass

to do work

due to its position in a gravitational field

near Earth’s surface,
∆Ep = mgh

OR
WD by ext agent in bringing a mass from inf to that pt

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44
Q

Elastic Potential Energy

A

energy stored in a body

due to a force

causing its deformation

for a spring that obey’s Hooke’s law,
Ep = 1/2 kx²

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45
Q

Principle of Conservation of Energy

A

The principle of conservation of energy states that

energy cannot be created or destroyed - it can only be converted from one form to another.

The total energy of an isolated system remains constant.

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46
Q

Power

A

work done per unit time

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47
Q

Efficiency

A

the percentage ratio of useful work output to total energy input
v

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48
Q

Radian (unit)

A

one radian is

the angle subtended at the centre of a circle by an arc length

that is equal to the radius

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49
Q

Angular Displacement

A

the angle swept out by a radius

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50
Q

Angular Velocity

A

rate of change of angular displacement

swept out by radius

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51
Q

Centripetal Force

A

the resultant force acting on a body

towards the centre of a path curvature

which causes it to move in a circular path

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52
Q

Gravitational Field

A

a region of space

where a mass

experiences a gravitational force

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53
Q

Newton’s Law of Gravitation

A

Newton’s Law of gravitation states that the

[type of force] gravitational force of attraction between two point masses

[magnitude] is directly proportional to the product of the masses and

inversely proportional to the square of separation
between the masses

F = G (m₁m₂/r²)

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54
Q

Gravitational Field Strength

A

gravitational field strength at a point in the field is the

[type of force] gravitational force of attraction

[ratio] per unit mass

[specifics] by a small test mass placed at that point

g = G (M/r²)

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55
Q

Gravitational Potential

A

gravitational potential φ at a point in the field is the

[process] work done

[ratio] per unit mass

[specifics] in bringing a small test mass

from infinity to that point (without a change in kinetic energy)

φ = -G (M/r)

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56
Q

Geostationary Satellites

A
  • have a period of 24 hour
  • be in circular orbit at a particular radius
  • orbit directly above Equator
  • move from west to east along same orbital axis as Earth’s rotation
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57
Q

Thermal Equilibrium

A

no net flow of thermal energy

between the bodies that are in thermal contact

because they are at equal temperature

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58
Q

Heat

A

thermal energy that flows

from a region of higher temperature

to a region of lower temperature

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59
Q

Thermometric Property

A

a property of a substance

that changes with temperature

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60
Q

Absolute Zero

A

a fixed point

on the absolute temperature scale

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61
Q

Ideal Gas Law

A

Ideal Gas Law states that

an ideal gas obeys the equation of state
pV = nRT

at all pressures, volumes and temperature

where p is the pressure due to gas, V is the volume the gas occupies, n is the quantity of gas, T is the temperature of gas, and R is the molar gas constant.

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62
Q

Assumptions behind the Kinetic Theory of Gases

A

a) Gas molecules are hard, elastic identical spheres
b) Large numbers of gas molecules are in continuous random motion
c) No intermolecular forces except during collisions
d) Total volume of molecules negligible compared to volume of containing vessel
e) Time of collisions negligible compared to time between collisions

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63
Q

Temperature

A

a measure of the average kinetic energy of particles in a system

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64
Q

Specific Heat Capacity

A

thermal energy per unit mass

to raise the temperature of a substance by one degree

c = Q / (m ∆T)

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65
Q

Specific Latent Heat of Fusion

A

thermal energy required per unit mass to convert a substance

from solid phase to liquid phase

at constant temperature

L = Q/m

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66
Q

Specific Latent Heat of Vaporisation

A

thermal energy required per unit mass to convert a substance

from liquid phase to gas phase

at constant temperature

L = Q/m

67
Q

[TESTED]** Internal Energy **[2021]

A

sum of kinetic energy

due to random motion of a distribution of particles and

potential energies

due to intermolecular forces between the particles

68
Q

First Law of Thermodynamics

A

the increase in internal energy of a system is the
sum of

heat supplied to system and

work done on system
∆U = Q + W

69
Q

Isobaric Process

A

a process where

the enclosed gas remains at constant pressure

70
Q

Isovolumetric Process

A

a process where

the enclosed gas remains at constant volume

71
Q

Isothermal Process

A

a process where

the enclosed gas remains at constant temperature

72
Q

Adiabatic Process

A

a process which

takes place with no heat supplied to or lost from the system

73
Q

Oscillation

A

a complete

to-and-fro motion

between two limits

74
Q

Free Oscillations

A

oscillations with constant amplitude

without energy loss or gain

as there is no external orce acting on the system

75
Q

Natural Frequency

A

frequency at which a system vibrates

in the absence of net external forces

76
Q

Equilibrium position

A

position of mass

where no net force acts on the oscillating mass

77
Q

Amplitude

A

maximum displacement from equilibrium position

in either direction of oscillating mass

78
Q

Phase angle

A

an angular measure

of the fraction of a cycle

completed by the oscillating mass

79
Q

Simple Harmonic Motion

A

Simple Harmonic Motion

80
Q

Simple Harmonic Motion

A

a type of oscillatory motion where

acceleration is directly proportional to displacement from equilibrium position and

directed opposite to displacement

a = -ω²x

81
Q

Damped oscillations

A

oscillations where the amplitude decreases exponentially with time

because of continuous loss of energy to surroundings due to negative work done against resistive forces

so the total energy in the system decreases with time

82
Q

Light Damping

A

when there is small resistive forces and the period remains
constant

83
Q

Critical Damping

A

when no oscillations occur and

displacement is brought to zero in shortest possible time

84
Q

Heavy Damping

A

when there is large resistive forces which greatly increases time

for displacement to be brought to zero without any oscillation

85
Q

Forced Oscillations

A

oscillations where there is

continuous input of energy

by external periodic force that

maintains the oscillation amplitude

86
Q

Resonance

A

when the driving frequency of external periodic force equals the natural frequency of the system

the resulting amplitude is maximum because
there is maximum rate of transfer of energy
from the external driver to the oscillating system

87
Q

Progressive Waves

A

energy is propagated from one place

to another

in the direction of wave travel

without bulk movement of medium

88
Q

Speed (of a wave)

A

speed at which energy is transferred

v = f λ

89
Q

Wavelength

A

minimum distance between

two points with the same phase

90
Q

Transverse wave

A

a wave where

oscillations are normal to the

direction of energy propagation

91
Q

Longitudinal wave

A

a wave where

oscillations are parallel to the

direction of energy propagation

92
Q

Intensity (of a wave)

A

rate of energy flow

per unit area that is perpendicular

to the direction of wave propagation

I = P/A

93
Q

Polarised Wave

A

in a polarised wave,

the oscillations are along one direction only,

in a single plane that is
normal to the direction of energy transfer of the wave

*Only transverse waves can be polarised

94
Q

Principle of Superposition

A

the principle of superposition states that

when two or more waves meet and overlap the resultant displacement is the

vector sum of the displacement of each individual wave

95
Q

Interference

A

when 2 or more waves meet and overlap,

the resultant displacement is the vector sum of
the displacement of each individual wave

giving rise to a pattern
of maximas and minimas

96
Q

[TESTED]** Diffraction **[2020]** **[2021]

A

the spreading of a wave

into geometric shadow

when it passes through a slit or past an edge of an obstacle

97
Q

Rayleigh Criterion

A

the rayleigh criterion states that the

limit for which 2 sources of light can be just distinguished
is when the

first minima of the diffraction pattern of one source
coincides with the

central maxima of the diffraction pattern of the other source

θ ≈ λ / b

98
Q

Coherent waves

A

waves where there is a constant phase difference
between the waves

99
Q

[TESTED]** Formation of stationary waves **[2020]

A

a stationary wave is formed when

two waves of the same type, same amplitude, same frequency, wavelength and speed,

travelling in opposite directions towards each other,

meet and overlap
Stationary vs Progressive wave

100
Q

Stationary vs Progressive wave in terms of wave profile

A

Progressive: advances in the direction of energy transfer of the wave

Stationary: does not advance
Stationary vs Progressive wave

101
Q

Stationary vs Progressive wave in terms of wavelength

A

Progressive: distance between adjacent points on the wave having same phase

Stationary: twice the distance between 2 adjacent nodes/ antinodes

102
Q

Stationary vs Progressive wave in terms of energy

A

Progressive: transferred in the direction of wave propagation

Stationary: kept within wave as KE and PE of vibrating particles
Stationary vs Progressive wave

103
Q

Stationary vs Progressive wave in terms of
amplitude of oscillation of individual particles

A

Progressive: same for all particles in the wave regardless of position (assuming no energy loss)

Stationary: varies from zero at nodes to maximum at antinodes
Stationary vs Progressive wave

104
Q

Stationary vs Progressive wave in terms of frequency

A

Progressive: all points oscillate at frequency of wave

Stationary: except at nodes, all points oscillate with at same frequency as the incident or reflected progressive wave

105
Q

Stationary vs Progressive wave
in terms of phase of wave particles

A

Progressive: all particles within one wavelength have different phases ranging from 0 to 2

Stationary: all particles within 2 adjacent nodes oscillate in phase; particles on either sides of a node oscillate in anti-phase

106
Q

Mode of Oscillation

A

a particular pattern of nodes and antinodes

107
Q

Fundamental Frequency

A

the lowest possible frequency of the standing wave

(or the longest possible wavelength of the incident/reflected wave)

108
Q

Overtone

A

the next possible mode of higher frequency from the fundamental mode

109
Q

Harmonics

A

integer relation of the frequency to the fundamental frequency

110
Q

Electric field

A

a region of space where a stationary charge experiences an electric force

111
Q

Field lines

A

lines that show the direction in which
a free positive charge will move

direction of electric field lines is from region of higher electric potential
to region of lower electric potential

112
Q

Coulomb’s Law

A

Coulomb’s Law states that the

[type of force] electric force between two point charges is

[magnitude] directly proportional to product of the two charges and

inversely proportional to the square of separation
between the two charges

F = 1 / (4πε₀) * Q₁Q₂ / r²

113
Q

Electric field strength

A

[type of force] electric force

[ratio] per unit positive charge

[specifics] on a small stationary test charge at that point

E = F / Q

114
Q

Electric potential

A

work done per unit positive charge

in moving a small test charge

from infinity to that point

V = U / Q

115
Q

Electric potential energy

A

work done in moving an electric charge

from infinity to that point in the electric field

116
Q

Equipotential Lines

A

lines joining points in a field

that have the same potential

(equipotential lines always meet electric field lines at right angles)

117
Q

Electric current

A

rate of flow of charge

118
Q

Drift velocity

A

the net velocity of charge carriers

in a certain direction under an externally-applied electric field

119
Q

Electromotive force

A

the energy transformed

from chemical to electrical

per unit charge that is

driven around a complete circuit

120
Q

Potential difference

A

the energy transformed

from electrical to other forms

per unit charge that is

passing through the component

V = W / Q

121
Q

Resistance

A

the ratio of

potential difference across component

to the current passing through it

R = V / I

122
Q

Ohm (unit)

A

1 Ohm is the resistance of a conductor

when the potential difference across it is 1 V and

the current flowing through it is 1 A.

123
Q

Maximum power transfer theorem

A

The maximum power transfer theorem states that maximum power transfer happens when

resistance of external load

is the same resistance

as the internal resistance of source of e.m.f.

124
Q

Magnetic field

A

a region of space in which

a permanent magnet,

a current-carrying conductor or

a moving charge

may experience a force

125
Q

[TESTED]** Magnetic Flux Density **[2020]** **[2021]

A

force per unit current

per unit length of wire

carrying a current is that normal to the magnetic field

B = F/ (I L sin 90°)

126
Q

Tesla (unit)

A

One tesla is the uniform magnetic flux density which,

acting normally to a long straight wire

carrying a current of 1 ampere,

causes a force per unit length of 1 Nm-1

to act on the conductor

127
Q

Magnetic Flux

A

product of an area and

component of magnetic flux density perpendicular to the area

Φ = B A cosθ

128
Q

Magnetic Flux Linkage

A

(magnetic flux linkage through a loop is)

product of magnetic flux through the loop and

number of turns of wire in the loop

magnetic flux linkage = N Φ = N B A cosθ

129
Q

Weber (unit)

A

one weber is

the magnetic flux

through an area of one squared metre

when the magnetic flux density normal to the area is one tesla

130
Q

[TESTED]** Faraday’s Law **[2020]

A

Faraday’s Law states that

the induced e.m.f.

is directly proportional to the

rate of change of magnetic flux linkage

131
Q

Lenz’s Law

A

Lenz’s Law states that

the direction of induced e.m.f.

produces effects to oppose the change causing it

132
Q

Peak value (amplitude)

A

maximum value of the a.c. in either direction within a cycle

133
Q

Peak-to-peak value

A

difference between the positive peak value and the negative peak value of the a.c. within a cycle

134
Q

Mean value

A

average value of an a.c. over a given time interval

135
Q

Root-mean-square (r.m.s.) value

A

value of a steady direct current that will

dissipate thermal energy

at the same average rate

as the a.c. in a given resistor

136
Q

Ideal transformer

A

a transformer with no power loss, so

input power is equal to the output power.

137
Q

[TESTED]** Photon **[2020]

A

a discrete packet of energy of electromagnetic radiation

The energy of one photon is directly proportional to the frequency of electromagnetic radiation

E = h f

138
Q

The Photoelectric Effect

A

the emission of electrons when

electromagnetic radiation of high-enough frequency is incident on a cold metal surface

139
Q

Work Function Φ

A

the minimum energy needed to

remove the least tightly bound electron from the surface of a metal

140
Q

Threshold frequency f₀

A

the minimum frequency of electromagnetic radiation for electrons to be emitted from the metal surface

h f₀ = Φ

141
Q

Stopping potential

A

the minimum potential difference between

the emitting metal and collector that

prevents the most energetic photoelectrons from reaching the collector plate,

resulting in zero photoelectric current

½ m v² = eV

where V is stopping potential

142
Q

Absorption line spectra

A

a continuous spectrum crossed by dark lines

143
Q

Emission line spectra

A

discrete bright lines of different colours on a dark background

144
Q

de Broglie wavelength

A

the wavelength of the matter wave that is associated with a particle that is moving

for a particle with momentum p, its associated wavelength is

λ = h / p

145
Q

Nuclide

A

a specific combination of protons and neutrons in a nucleus

146
Q

Nucleon

A

protons and neutrons in a nucleus

147
Q

Nucleon number, A (mass number)

A

total number of protons and neutrons in a nucleus

148
Q

Proton number, Z

(atomic number)

A

number of protons in a nucleus

149
Q

Neutron number, N

A

number of neutrons in a nucleus

N = A − Z

where A is nucleon number and Z is proton number

150
Q

Isotopes

A

nuclei of atoms of the same element

containing the same number of protons

but different number of neutrons

151
Q

Unified Atomic Mass Constant, u

A

one-twelfth of the mass of a neutral carbon-12 atom

152
Q

Mass Defect

A

difference between
total mass of individual,

separate nucleons and

the mass of the nucleus

153
Q

[TESTED]** Nuclear Binding Energy **[2020]

A

minimum energy required

to completely separate
protons and neutrons in a nucleus

and bring them to infinity

binding energy = ∆m c²

154
Q

Nuclear Fusion

A

[action] combining of two or more light nuclei

[condition] under very high temperatures

[result] to form a single, more massive nucleus

155
Q

Nuclear Fission

A

[action] splitting of a single heavy nucleus

[condition] when bombarded by neutrons

[result] to form two or more lighter nuclei
of approximately same mass

with neutrons emitted

156
Q

ionising power

A

the ability of the radiation to

remove electrons from other atoms

157
Q

Radioactive Decay

A

[nature] spontaneous and random

[action] emission of ionising radiation in the form alpha particles, beta particles or gamma ray photons

[initial & final] from unstable nucleus to become a more stable nucleus

158
Q

Spontaneous Process

A

a process not triggered or affected by external factors such as

temperature and pressure

159
Q

Random Process

A

a process with constant probability of decay of a nucleus

per unit time and

the time of decay of a nucleus cannot be predicted

160
Q

Decay Constant, λ

A

probability of decay
of an unstable nucleus
per unit time interval

161
Q

Activity, A

A

(activity of a sample is the) rate at which unstable nuclei decay

A = λN

162
Q

Half-life

A

average time for the activity or

number of unstable nuclei

to be reduced to one half of initial value

t₁/₂ = ln(2) / λ

163
Q

Line spectra providng evidence of discrete energy levels

A

Dark/bright lines correspond with the
freq/wavelength of the photon of a specific energy E=hf that is
emitted/absorbed when orbital e
undergo specific energy changes when
deexciting/promoting between discrete energy levels

A level physics formulas (2 decks)

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