Vocabulary Flashcards
Accuracy
An accurate value of a measured quantity is one which is close to the true value of the quantity
Amplitude
The maximum displacement of a particle for its equilibrium position
Antinode
A point on a stationary wave with maximum displacement or amplitude
Atomic mass unit
A unit of mass (u) approximately equal to 1.661 x 10-27 kg.
The mass of an atom of 12-carbon = 12.000u exactly
Average speed
The total distance travelled by an object divided by the total time taken
Avogadro constant
The number of particles in one mole of any substance, 6.02 x 10^23 mol-1
Base unit
Defined units of the SI system from which all other units are derived
Best fit line
A straight line drawn as closely as possible to the points of a graph so that similar numbers of points lie above and below the line
Centre of gravity
The point where the entire weight of an object appears to act
Charge carrier
Any charged particle, such as an electron, responsible for a current, and an ion
Closed system
A system of interacting objects in which there are no external forces
Coherent
Two sources are coherent when they emit waves with a constant phase different
Acceleration
The rate of change of an object’s velocity
a = v/t
Unit: ms-2
Components (of vector)
The magnitudes of a vector quantity in two perpendicular direction
Compression
A region in a sound wave where the air pressure is greater than its mean value
Compressive
Decries a force that squeezes an object
Conservation of momentum
In a closed system, when bodies interact, the total momentum in any specified direction remains constant
Constructive interference
When two waves reinforce to give increased amplitude
contact force
the force an object exerts on another with which it is in contact
coulomb
the SI unit of electrical charge (C). a charge of 1 C passes a point when a current of 1 A flows for 1 s.
1 C = 1 A s
couple
a pair of equal and antparallel forces having a turning effect but no resultant force
density
the mass per unit volume of a material:
density = m/V
Unit: kg m-3
derived units
units which are combinations of the base units of the SI system
destructive interference
when two waves cancel to give reduced amplitude
diffraction
the spreading of a wave when it passes through a gap or past the edge of an object
dispersion
the splitting of light into its different wavelengths
displacement
the distance moved by an object in a particular direction measured from a fixed starting point
Dopple effect
the change in frequency or wavelength of a wave observed when the source of the wave is moving relatively towards or away from the observer, or the observer is moving relative to the source
drage
a force that resists the movement of a body through a fluid
mean drift velocity
the average speed of a collection of charged particles when a current flows
dynamics
the study of motion using quantities such as force and mass
e.m.f.
the total work done when unit charge is moved round a complete circuit.
Unit: J C-1 or V
1 V = 1 J C-1
efficiency
the ratio of useful output energy to the total input energy for a device, expressed as a percentage:
efficiency = (useful output energy/total input energy) x 100%
elastic limit
the value of stress beyond which an object will not return to its original dimensions
elastic potential energy
energy stored in a stretched or compresses material
electric charge
a property of a body that gives rise to a force on the body when it is within an electric field
electric field
a region in which a charged body experiences a force
electric field strength
the force per unit positive charge at a point.
Unit: V m-1 or N C-1
electrical resistance
the ratio of potential difference to current.
Unit: ohm
electrolyte
an electrically conducting solution. the conduction is due to positive and negative ions in the solution
electromagnetic spectrum
the family of waves that travel through a vacuum at a speed of 3.00 x 10^8 m s-1
elementary charge
the smallest unit of charge that a particle or an object can have. it has a magnitude of 1.60 x 10-19 C
energy
a calculated quantity which is conserved during any change; that which is transferred when a force does wok
equation of motion
four interrelated equations that can be used to determine the displacement, initial velocity, final velocity and acceleration of a body moving with constant acceleration v = u + at s = ut + 1/2 at^2 s = 1/2 (u+v)t v^2 = u^2 + 2as s = vt - 1/2 at^2
equilibrium
an object in equilibrium is either at rest or travelling with a constant velocity because the resultant force on it is zero.
- no resultant force
- no resultant moment
errors
inaccuracies when taking measurements
extension
the change in the length of a material from its original length
field lines
lines drawn to represent the strength and direction of a field of force
field of force
a region of space where an object feels a force; the force may be gravitational, electric, magnetic, etc.
force constant
the ratio of force to extension for a spring or a wire.
Unit: N m-1
free-body force diagram
a diagram showing all the forces acting on an object (but not the forces it exerts on other objects)
frequency
the number of oscillations per unit time.
Unit: hertz (Hz)
fundamental frequency
the lowest-frequency stationary wave for a particular system
hadron
any particle which is affected by the strong nuclear force, made from two or three quarks or anti-quarks
harmonic
a wave of frequency n times the fundamental frequency, where n is an integer
Hooke’s law
the extension produced in an object is proportional to the force producing it
independent variable
the variable in an experiment which a value that is altered by the experimenter
inelastic
a collision is inelastic when kinetic energy is not conserved; some is transferred to other forms such as heat. Momentum and total energy are always conserved
inertia
a measure of the mass of an object. a massive object has large inertia
instantaneous speed
the speed of an object measured over a very short period of time
intensity
the power transmitted normally through a surface per unit area:
intensity = power/cross-sectional area
unit: W m-2
interference
the formation of points of cancellation and reinforcement where two coherent waves pass through each other
internal energy
the sum of the random distribution of kinetic and potential energies of the atoms or molecules in a system
internal resistance
the resistance of an e.m.f. source. the internal resistance of a battery is due to the chemicals within it.
ion
an atom with a net positive or negative charge
isotopes
nuclei of the same element with a different number of neutrons but the same number of protons
I-V characteristic
a graph of current against voltage for a particular component of an electrical circuit
kinematics
the study of motion using quantities such as time, distance, displacement, speed velocity and acceleration
kinetic energy energy of an object due to its moton
energy of an object due to its moton
Kirchhoff’s first law
the sum of the currents entering any point (or junction) in a circuit is equal to the the sum of the currents leaving that same point. this law represents the conservation of charge
Kirchhoff’s second law
the sum of the e.m.f.s round a closed loop in a circuit is equal to the sum of the p.d.s in that same loop
lepton
a sub-atomic particle which is not affected by the strong nuclear force
light-dependent resistor (LDR)
a resistor whose resistance decreases as the intensity of light falling on it increases
linear momentum
the product of an object’s mass and its velocity
p = mv
it is a vector quantity
longitudinal wave
a wave in which the particles of the medium oscillate along the direction in which the wave tracels
lost volts
the difference between the e.m.f. and the terminal p.d. in a circuit. it is equal to the voltage across the internal resistance
mass
a measure of the amount of matter with in an object
Unit: kg
mole
the amount of matter which contains 6.02 x 10^23 particles
moment
the moment of a force about a point is the magnitude of the force, multiplied by the perpendicular distance of the point from the line of the force.
Unit: N m
monochromatic
describes light of a single frequency
neutrino
a lepton, released during beta-decay
neutron number
the number of neutrons in the nucleus of an atom
newton
the force that will give a 1 kg mass an acceleration of 1 ms-2 in the direction of the force.
1 N = 1 kg m s-2
Newton’s first law of motion
an object will remain at rest or keep travelling at constant velocity unless it is acted on by a resultant force
Newton’s second law of motion
the resultant force acting on an object is equal to the rate of change of its momentum. the resultant force and the change in momentum are in the same direction
Newton’s third law of motion
when two bodies interact, the forces they exert on each other are equal and opposite.
node
a point on a stationary wave with zero amplitude
nucleon number / mass number
the number of neutrons and protons in the nucleus of an atom
nucleon
a particle found in an atomic nucleus, i.e. a neutron or a proton
nucleus
the tiny central region of the atom that contains most of the mass of the atom and all of its positive charge
number density
the number of particles, such as free electrons, per unit volume in a material
Ohm’s law
the current in a metallic conductor is directly proportional to the potential difference across its ends, provided its temperature remains constant
path difference
the difference in the distances travelled by two waves from coherent sources at a particular point
perfectly elastic
a collision is perfectly elastic when kinetic energy is conserved. momentum and total energy are always conserved
period
the time taken by an object (e.g. a planet) to complete one cycle (e.g. an orbit). the period is also the time taken for one complete oscillation of a vibrating object
Unit: second (s)
phase
refers to the point that an oscillation mass has reached in a complete cycle
phase difference
the difference in the phases of two oscillating particles, expressed in degrees or radians
plum-pudding model
a model of the atom in which negative charges are distributed throughout a sphere of positive charge
positron
an anti-electron
potential difference (p.d.)
the energy lost per unit charge by charges passing through a component.
Unit: J C-1 or volt (V)
potential divider
a circuit in which two or more components are connected in series to a supply. the output voltage from the circuit is taken across one of the components
potentiometer
a circuit which allows the measurement of an e.m.f. by comparison with a known e.m.f.
power
the rate at which energy is transferred or the rate at which work is done
precision
the smallest change in value that can be measured by an instrument or an operator. a precise measurement is one made several times, giving the same, or very similar, values
pressure
the force acting normally per unit area of a surface:
p = F/A
Unit: N m-2 or pascal (Pa)
principle of conservation of energy
the idea that, within a closed system, the total amount of energy in all its forms is unchanged during any change
principle of moments
for an object in equilibrium, the sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point
principle of superposition
when two or more waves meet at a point, the resultant displacement is the sum of the algebraic displacements of the individual waves
progressive wave
a wave that carries energy from one place to another
projectile
any object thrown in the earth’s gravitational field
proton number / atomic number
the number of protons in the nucleus of an atom
quarks
the fundamental particles of which hadrons are made
range
the horizontal distance covered by an object
rarefaction
a region in a sound wave where the air pressure is lass than its mean value
red shift
the change in frequency or wavelength of a spectral line observed when the source of light is moving away from the observer
relative speed
the magnitude of the ifference in velocities between two objects
resistivity
a property of a material, a measure of its electrical resistance, defined by:
resistivity = (RA) / L
Unit: ohm m
resistor
an electrical component whose resistance in a circuit remains constant, is independent of current or potential difference
resonance
the forced motion of an oscillator characterised by maximum amplitude when the forcing frequency matches the oscillator’s natural frequency. a system absorbs maximum energy from a source when the source frequency is equal to the natural frequency of the system
rest mass
the mass of an isolated stationary particle
resultant force
the single force that has the same effect as all of the forces acting on an object
scalar quantity
a scalar quantity has magnitude but no drection
series
a term used when components are connected end-to-end in a circuit
speed
the rate of change of the distance moved by an object:
speed = distance/time
Unit: m s-1
spin
a fundamental property of subatomic particles which is conserved during atomic and nuclear reactions
stationary wave
a wave pattern produced when two progressive waves of the same frequency traveling in opposite directions combine.
strain
the extension per unit length produced by tensile or compressive forces:
strain = extension / original length
strain energy
the potential energy stored in an object when it is deformed elastically
stress
the force actin per unit cross-sectional area:
stress = force / cross-sectional area
systematic error
an error in readings which is repeated throughout an experiment, producing a constant absolute error or a constant percentage error
tensile
associated with tension or pulling, e.g. a tensile force
terminal p.d.
the potential difference across an external resistor connected to an e.m.f. souce
terminal velocity
the maximum velocity of an object travelling through a fluid. the resultant force on the object is zero
thermistor
a device whose electrical resistance changes when its temperature changes.
decrease when temperature increases
torque of a couple
the product of one of the forces of a couple and the perpendicular distance between them.
Unit: N m
transverse wave
a wave in which the particles of the medium oscillate (the displacement of the particles is) at right angles to the direction in which the wave travels (the wave energy is transferred)
unified atomic mass unit
a convenient unit used for the mass of atomic and nuclear particles (1u is equal to the mass of a 12-carbon atom)
1u = 1.66 x 10^-27 kg
uniform acceleration
acceleration that remains constant
upthrust
the upward force that a liquid exerts on a body floating or immerse in a liquid
vector addition
using a drawing, often to scale to find the resultant of two or more vectors
vector quantity
a quantity which has both magnitude and direction
vector triangle
a triangle drawn to determine the resultant of two vectors
velocity
the rate of change of the displacement of an object:
velocity = change in displacement / time
Unit: m s-1
viscous forces
forces that act on a body moving through a fluid that are caused by the resistance of the fluid
wave
a periodic disturbance travelling through space, characterised by a vibrating medium
wavelength
the distance between two adjacent peaks or troughs in a wave
weak nuclear force
a fundamental force, involved in radioactive beta-decay
weight
the force on an object caused by a gravitational field acting on its mass:
weight = mass x acceleration of free fall
Unit: newton (N)
workdone
the product of the force and the distance moved in the direction of the force
Young modulus
the ratio of stress to strain for a given material, resulting from tensile forces, provided Hooke’s law is obeyed:
Young modulus = stress / strain
Unit: pascal (Pa; or MPa, GPa)
zero error
a systematic error in an instrument that gives a non-zero reading when the true value of a quantity is zero
nuclide
a specific combination of protons and neutrons in a nucleus
