Definitions Flashcards
Random Error
when the
measured readings are
scattered about the true reading
with no fixed pattern
Systematic Error
when the
measured readings are
consistently larger
or consistently smaller
than the true reading
Accuracy
how close the measured reading is
to the true value
Precision of a set of readings
how close the measured readings are
to each other
Precision of an instrument
the size of the smallest division
scalar quantity
a physical quantity that has magnitude only
vector quantity
a physical quantity that has both magnitude and direction
Displacement
[magnitude] minimum straight line distance between start and endpoints
[direction] in that direction
Distance
length of actual path followed
Velocity
rate of change of displacement
Speed
rate of change of distance
Acceleration
rate of change of velocity
[TESTED]** Newton’s First Law of Motion **[2020]
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
Newton’s Second Law of Motion
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
Newton’s Third Law of Motion
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.
Mass of a body
property of a body which resists change in motion
Weight of a body
force acting on the body due to a gravitational field
Linear Momentum
product of its mass and velocity
p = mv
Force
rate of change of momentum
F = dp/dt
Impulse
product of resultant force and
time duration of impact
∆p = Fnet ∆t
The Principle of Conservation of Linear Momentum
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
Perfectly elastic collisions (distinguishing property)
total kinetic energy of the system of bodies
before and after collision remains the same
[TESTED]** Inelastic collisions (distinguishing property) **[2020]
total kinetic energy of system of bodies
after collision is less than before
[TESTED]** Perfectly inelastic collisions (distinguishing property) **[2020]
masses stick together and
move off with same velocity after collision
[TESTED]** Field of a Force **[2020]
a region of space in which a force acts on a particle
Centre of Gravity
the single point where
the weight of a body may be considered to act
Moment of a Force
he product of the force and the
perpendicular distance to the pivot
from the line of action
Couple
a pair of forces that are
equal in magnitude and
opposite in direction
that does not act along the same line of action
Torque of a Couple
product of one of a pair forces and
the perpendicular distance between the forces
torque = F x d
Translational Equilibrium
[magnitude] no resultant force
[direction] in any direction
Rotational Equilibrium ———————————————- [magnitude] no resultant torque
[direction] about any point
Equilibrium
when there is no resultant force in any direction and
there is no resultant torque about any point
Principle of Moments
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
Hooke’s Law
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
Pressure
force acting normally
per unit area of a surface
p = F/A
Upthrust
a force
equal in magnitude and
opposite in direction to the
weight of fluid displaced by submerged or floating object
Tension
a force
along the length of a body
Friction
a force
that opposes relative motion between surfaces in contact.
It can also act to oppose
impending relative motion of surfaces.
Normal Contact Force
a force
exerted perpendicular to surfaces
that are physically touching
Viscous Force
a dissipative force that
acts when there is relative motion
between a body and the fluid (either a gas or liquid) surrounding the body.
Lift
a force
which acts perpendicular to the
direction of relative flow of surrounding fluid
when there is relative motion
between body and fluid
Work Done
the product of the force and
the displacement in the direction of the force
W = Fscosθ
(Translational) Kinetic Energy
the ability of a mass
to do work
due to its speed
Ek = 1/2 mv²
[TESTED]** Gravitational Potential Energy **[2020]
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
Elastic Potential Energy
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
Principle of Conservation of Energy
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.
Power
work done per unit time
Efficiency
the percentage ratio of useful work output to total energy input
v
Radian (unit)
one radian is
the angle subtended at the centre of a circle by an arc length
that is equal to the radius
Angular Displacement
the angle swept out by a radius
Angular Velocity
rate of change of angular displacement
swept out by radius
Centripetal Force
the resultant force acting on a body
towards the centre of a path curvature
which causes it to move in a circular path
Gravitational Field
a region of space
where a mass
experiences a gravitational force
Newton’s Law of Gravitation
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)
Gravitational Field Strength
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)
Gravitational Potential
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)
Geostationary Satellites
- 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
Thermal Equilibrium
no net flow of thermal energy
between the bodies that are in thermal contact
because they are at equal temperature
Heat
thermal energy that flows
from a region of higher temperature
to a region of lower temperature
Thermometric Property
a property of a substance
that changes with temperature
Absolute Zero
a fixed point
on the absolute temperature scale
Ideal Gas Law
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.
Assumptions behind the Kinetic Theory of Gases
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
Temperature
a measure of the average kinetic energy of particles in a system
Specific Heat Capacity
thermal energy per unit mass
to raise the temperature of a substance by one degree
c = Q / (m ∆T)
Specific Latent Heat of Fusion
thermal energy required per unit mass to convert a substance
from solid phase to liquid phase
at constant temperature
L = Q/m
Specific Latent Heat of Vaporisation
thermal energy required per unit mass to convert a substance
from liquid phase to gas phase
at constant temperature
L = Q/m
[TESTED]** Internal Energy **[2021]
sum of kinetic energy
due to random motion of a distribution of particles and
potential energies
due to intermolecular forces between the particles
First Law of Thermodynamics
the increase in internal energy of a system is the
sum of
heat supplied to system and
work done on system
∆U = Q + W
Isobaric Process
a process where
the enclosed gas remains at constant pressure
Isovolumetric Process
a process where
the enclosed gas remains at constant volume
Isothermal Process
a process where
the enclosed gas remains at constant temperature
Adiabatic Process
a process which
takes place with no heat supplied to or lost from the system
Oscillation
a complete
to-and-fro motion
between two limits
Free Oscillations
oscillations with constant amplitude
without energy loss or gain
as there is no external orce acting on the system
Natural Frequency
frequency at which a system vibrates
in the absence of net external forces
Equilibrium position
position of mass
where no net force acts on the oscillating mass
Amplitude
maximum displacement from equilibrium position
in either direction of oscillating mass
Phase angle
an angular measure
of the fraction of a cycle
completed by the oscillating mass
Simple Harmonic Motion
Simple Harmonic Motion
Simple Harmonic Motion
a type of oscillatory motion where
acceleration is directly proportional to displacement from equilibrium position and
directed opposite to displacement
a = -ω²x
Damped oscillations
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
Light Damping
when there is small resistive forces and the period remains
constant
Critical Damping
when no oscillations occur and
displacement is brought to zero in shortest possible time
Heavy Damping
when there is large resistive forces which greatly increases time
for displacement to be brought to zero without any oscillation
Forced Oscillations
oscillations where there is
continuous input of energy
by external periodic force that
maintains the oscillation amplitude
Resonance
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
Progressive Waves
energy is propagated from one place
to another
in the direction of wave travel
without bulk movement of medium
Speed (of a wave)
speed at which energy is transferred
v = f λ
Wavelength
minimum distance between
two points with the same phase
Transverse wave
a wave where
oscillations are normal to the
direction of energy propagation
Longitudinal wave
a wave where
oscillations are parallel to the
direction of energy propagation
Intensity (of a wave)
rate of energy flow
per unit area that is perpendicular
to the direction of wave propagation
I = P/A
Polarised Wave
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
Principle of Superposition
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
Interference
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
[TESTED]** Diffraction **[2020]** **[2021]
the spreading of a wave
into geometric shadow
when it passes through a slit or past an edge of an obstacle
Rayleigh Criterion
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
Coherent waves
waves where there is a constant phase difference
between the waves
[TESTED]** Formation of stationary waves **[2020]
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
Stationary vs Progressive wave in terms of wave profile
Progressive: advances in the direction of energy transfer of the wave
Stationary: does not advance
Stationary vs Progressive wave
Stationary vs Progressive wave in terms of wavelength
Progressive: distance between adjacent points on the wave having same phase
Stationary: twice the distance between 2 adjacent nodes/ antinodes
Stationary vs Progressive wave in terms of energy
Progressive: transferred in the direction of wave propagation
Stationary: kept within wave as KE and PE of vibrating particles
Stationary vs Progressive wave
Stationary vs Progressive wave in terms of
amplitude of oscillation of individual particles
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
Stationary vs Progressive wave in terms of frequency
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
Stationary vs Progressive wave
in terms of phase of wave particles
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
Mode of Oscillation
a particular pattern of nodes and antinodes
Fundamental Frequency
the lowest possible frequency of the standing wave
(or the longest possible wavelength of the incident/reflected wave)
Overtone
the next possible mode of higher frequency from the fundamental mode
Harmonics
integer relation of the frequency to the fundamental frequency
Electric field
a region of space where a stationary charge experiences an electric force
Field lines
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
Coulomb’s Law
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
Electric field strength
[type of force] electric force
[ratio] per unit positive charge
[specifics] on a small stationary test charge at that point
E = F / Q
Electric potential
work done per unit positive charge
in moving a small test charge
from infinity to that point
V = U / Q
Electric potential energy
work done in moving an electric charge
from infinity to that point in the electric field
Equipotential Lines
lines joining points in a field
that have the same potential
(equipotential lines always meet electric field lines at right angles)
Electric current
rate of flow of charge
Drift velocity
the net velocity of charge carriers
in a certain direction under an externally-applied electric field
Electromotive force
the energy transformed
from chemical to electrical
per unit charge that is
driven around a complete circuit
Potential difference
the energy transformed
from electrical to other forms
per unit charge that is
passing through the component
V = W / Q
Resistance
the ratio of
potential difference across component
to the current passing through it
R = V / I
Ohm (unit)
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.
Maximum power transfer theorem
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.
Magnetic field
a region of space in which
a permanent magnet,
a current-carrying conductor or
a moving charge
may experience a force
[TESTED]** Magnetic Flux Density **[2020]** **[2021]
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°)
Tesla (unit)
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
Magnetic Flux
product of an area and
component of magnetic flux density perpendicular to the area
Φ = B A cosθ
Magnetic Flux Linkage
(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
Weber (unit)
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
[TESTED]** Faraday’s Law **[2020]
Faraday’s Law states that
the induced e.m.f.
is directly proportional to the
rate of change of magnetic flux linkage
Lenz’s Law
Lenz’s Law states that
the direction of induced e.m.f.
produces effects to oppose the change causing it
Peak value (amplitude)
maximum value of the a.c. in either direction within a cycle
Peak-to-peak value
difference between the positive peak value and the negative peak value of the a.c. within a cycle
Mean value
average value of an a.c. over a given time interval
Root-mean-square (r.m.s.) value
value of a steady direct current that will
dissipate thermal energy
at the same average rate
as the a.c. in a given resistor
Ideal transformer
a transformer with no power loss, so
input power is equal to the output power.
[TESTED]** Photon **[2020]
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
The Photoelectric Effect
the emission of electrons when
electromagnetic radiation of high-enough frequency is incident on a cold metal surface
Work Function Φ
the minimum energy needed to
remove the least tightly bound electron from the surface of a metal
Threshold frequency f₀
the minimum frequency of electromagnetic radiation for electrons to be emitted from the metal surface
h f₀ = Φ
Stopping potential
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
Absorption line spectra
a continuous spectrum crossed by dark lines
Emission line spectra
discrete bright lines of different colours on a dark background
de Broglie wavelength
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
Nuclide
a specific combination of protons and neutrons in a nucleus
Nucleon
protons and neutrons in a nucleus
Nucleon number, A (mass number)
total number of protons and neutrons in a nucleus
Proton number, Z
(atomic number)
number of protons in a nucleus
Neutron number, N
number of neutrons in a nucleus
N = A − Z
where A is nucleon number and Z is proton number
Isotopes
nuclei of atoms of the same element
containing the same number of protons
but different number of neutrons
Unified Atomic Mass Constant, u
one-twelfth of the mass of a neutral carbon-12 atom
Mass Defect
difference between
total mass of individual,
separate nucleons and
the mass of the nucleus
[TESTED]** Nuclear Binding Energy **[2020]
minimum energy required
to completely separate
protons and neutrons in a nucleus
and bring them to infinity
binding energy = ∆m c²
Nuclear Fusion
[action] combining of two or more light nuclei
[condition] under very high temperatures
[result] to form a single, more massive nucleus
Nuclear Fission
[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
ionising power
the ability of the radiation to
remove electrons from other atoms
Radioactive Decay
[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
Spontaneous Process
a process not triggered or affected by external factors such as
temperature and pressure
Random Process
a process with constant probability of decay of a nucleus
per unit time and
the time of decay of a nucleus cannot be predicted
Decay Constant, λ
probability of decay
of an unstable nucleus
per unit time interval
Activity, A
(activity of a sample is the) rate at which unstable nuclei decay
A = λN
Half-life
average time for the activity or
number of unstable nuclei
to be reduced to one half of initial value
t₁/₂ = ln(2) / λ
Line spectra providng evidence of discrete energy levels
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
