Definitions

Key words and Definitions needed for AS Physics.

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a physical quantity which has magnitude only
scalar
1 of 77
a physical quantity which has both magnitude and direction
vector
2 of 77
distance from a fixed point in a specified direction
displacement
3 of 77
Mechanics - rate of change of distance withe respect to time
speed
4 of 77
rate of change of displacement with respect to time
velocity
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rate of change of velocity with respect to time
acceleration
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gravitational force on a mass in a gravitational field
weight
7 of 77
constant maximum velocity reached when drag force becomes equal to weight for an object
terminal velocity
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point where all the weight of a object appears to act
centre of gravity
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force x perpendicular distance from the line of the force to point
moment of a force
10 of 77
resultant moment about any point =0
equilibrium
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for an object in equilibrium, the sum of clockwise moments = sum of anti-clockwise moments about any point
principle of moments
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mass per unit volume
density
13 of 77
force / area perpendicular to the force
pressure
14 of 77
distance travelled between seeing object and pressing brake
thinking distance
15 of 77
distance travelled between applying brake and coming to rest
braking distance
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thinking distance + braking distance
stopping distance
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force x distance moved in direction of force
work done
18 of 77
1N x 1m
joule
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for a closed system, total energy remains constant
principle of conservation of energy
20 of 77
energy of movement
kinetic energy
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work done per unit time
power
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1J / 1s
watt
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useful power out / total power in
efficiency
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up to elastic limit, force is directly proportional to extension
hooke's law
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point beyond which a spring will not return to its original length when the force is removed
elastic limit
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energy stored in a stretched object
elastis potential energy
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extending force / cross sectional area
stress
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extension / original length
strain
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stress / strain
young's modulus
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object returns to its original size and shape after deforming forces removed
elastic
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object doesn't return to its original size and shape after deforming forces removed
plastic
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breaks/shatters into sharp fragments (no plastic region)
brittle
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can be drawn into a wire (must have plastic region)
ductile
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long chain molecules made from repeating units e.g. rubber
polymer
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net flow of electric charge
current
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At any junction, sum of currents in = sum of currents out
kirchoff's first law
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mean displacement of charge carriers per unit time
mean drift velocity
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energy converted per unit charge from electrical energy to other forms of energy in a load
potential difference
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1J / 1C
volt
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energy converted per unit charge to electrical energy from other forms of energy in a source
emf
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potential difference / current
resistance
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1V / 1A
ohm
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foe a metallic conductor at constant temperature, PD is directly proportional to current
ohm's law
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(resistance x cross sectional area) / length
resistivity
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energy converted by a device of power 1kW operating for a time of 1 hour
kilowatt hour
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around any closed loop, sum of PDs = sum of Emfs
kirchoff's second law
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particles oscillate parallel to direction of travel of the wave
longitudinal
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particles oscillate perpendicular to direction of travel of the wave
transverse
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distance moved from equillibrium position in a specified direction
particle displacement in wave
50 of 77
maximum displacement
amplitude
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distance between two successive points on a wave that are in phase
wavelength
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time for 1 complete oscillation of a particle
period
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number of oscillations per unit time
frequency
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distance travelled by a wave per unit time
speed
55 of 77
wave bounces back from a surface
reflection
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wave changes direction as crossing a boundary between two media due to a change in speed
refraction
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wave spreads out as goes through a narrow gap, round a narrow obstacle or by a sharp edge
diffraction
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particles oscillate ina single plane (transverse only)
polarisation
59 of 77
when 2 or more waves overlap, resultant displacement is the vector sum of the individual displacements
principle of superposition
60 of 77
pattern of maximum and minimum produced when waves from 2 sources overlap (same wavelength and amplitude)
interference
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constant phase difference
coherence
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extra distance travelled by waves from one source compared to waves from another source
path difference
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Interference - maximum produced when waves reinforce
constructive
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Interference - minimum produced when waves cancel
destructive
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proportional to amplitude squared
intensity
66 of 77
point on standing wave where amplitude is zero
node
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point on standing wave where amplitude is at maximum
antinode
68 of 77
lowest frequency that produces a standing wave
fundamental mode of vibration
69 of 77
multiples of the fundamental frequency
harmonics
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the energy change when an electron moves through a PD of 1 volt
electron volt
71 of 77
when light shines on a clean metal surface electrons may be emitted
photoelectric effect
72 of 77
minimum energy needed to release an electron from the surface of metal
work function energy
73 of 77
minimum frequency needed to release a photoelectron
threshold frequency
74 of 77
light emitted from gases - discrete wavelengths
line spectrum
75 of 77
light emitted from solids - all wavelengths
continuous spectrum
76 of 77
allowed energy state of an atom
energy level
77 of 77

Other cards in this set

Card 2

Front

a physical quantity which has both magnitude and direction

Back

vector

Card 3

Front

distance from a fixed point in a specified direction

Back

Preview of the front of card 3

Card 4

Front

Mechanics - rate of change of distance withe respect to time

Back

Preview of the front of card 4

Card 5

Front

rate of change of displacement with respect to time

Back

Preview of the front of card 5
View more cards

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