Definitions Flashcards
(138 cards)
1
Q
Vector
A
A vector quantity has a magnitude AND a direction. e.g. Force, Velocity, Acceleration
2
Q
Scalar
A
A scalar quantity has a magnitude only. e.g. Mass, Charge, Energy,
3
Q
Displacement
A
The distance travelled in a particular direction.
4
Q
Velocity
A
The distance travelled in a particular direction per unit time.
5
Q
Speed
A
The distance travelled per unit time.
6
Q
Instantaneous Speed
A
The speed at any particular instant in time.
7
Q
Average Speed
A
The overall distance travelled divided by the time taken.
8
Q
Acceleration
A
The rate of change of velocity.
9
Q
1 Newton
A
The force on a 1 kg mass which is being accelerated by 1 ms^-2
10
Q
Drag Force/Frictional Force
A
The force on an object which opposes the motion of the object, or the tendency of the object to move.
11
Q
Weight
A
The gravitational force acting on an object.
12
Q
Terminal Velocity
A
The constant velocity of an object, achieved when the frictional forces balance the driving force.
13
Q
Moment of a Force or a Torque
A
A Turning or Rotational Force, given by the product of the Force and the perpendicular distance from the pivot point or axis of rotation.
14
Q
A Couple
A
A pair of equal but opposite forces with lines of action separated by a distance. The couple tends to produce rotation only.
15
Q
Torque of a couple
A
The product of one of the forces in a couple, and the perpendicular distance between them.
16
Q
Equilibrium
A
The state of an object such that the total force and total moment acting on it are zero.
17
Q
Stress
A
The applied force per unit area.
18
Q
Strain
A
The extension produced per unit length.
19
Q
Young’s Modulus
A
The stress per unit strain when a material is behaving elastically.
20
Q
Ultimate tensile strength/breaking stress/breaking strength
A
The maximum possible stress applied to a material before fracture.
21
Q
Elastic deformation
A
Deformation that can be fully recovered when the force on an object is removed.
22
Q
Plastic deformation
A
Deformation that can NOT be fully recovered when the force on an object is removed.
23
Q
Centre of Mass/Centre of Gravity
A
The point where the entire weight of an object appears to act.
24
Q
Thinking distance
A
The distance a vehicle will travel during the time the driver takes to see the problem and apply the brakes.
25
Thinking time
The time taken for the driver to see a problem and apply the brakes.
26
Braking distance
The distance taken for the vehicle to come to rest when the brakes are applied.
27
Stopping distance
The total distance taken for a vehicle to come to rest from the point where the incident is first seen. Given by the thinking distance plus the braking distance.
28
Work Done (by a Force)
The amount of energy converted from one form to another. The product of the applied force on an object and the distance over which the force is applied.
29
1 Joule
The kinetic energy a 2 kg mass has when it moves with a speed of 1 ms^-1. The gravitational potential energy a 0.1 kg mass has when held 1 m above the Earth's surface.
30
Conservation of Energy
For an isolated system, the total energy is a constant value. Energy cannot be created or destroyed, only converted from one form to another.
31
Power
The rate of work done/ the amount of work done per unit time.
32
1 Watt
The power of an engine which is converting 1 J of energy in 1 second.
33
Potential difference
The change of electrical potential energy into other forms, when 1 C of charge moves between two points.
34
Current
The positive charge flowing per unit time.
35
Electrical Resistance
The opposition to the flow of current. Given by the ratio of the voltage per unit amp. The voltage per unit current.
36
Resistivity
The resistance between the ends of a 1 m length of material which has a cross-sectional area of 1 m^2.
37
EMF.
The electrical potential energy per unit charge converted into other forms from a battery or power supply.
38
Potential Difference
The electrical potential energy change between two points in a circuit per unit charge.
39
1 Coulomb
The amount of charge flowing in 1 second when a current of 1 A flows.
40
1 Volt
The potential difference across a 1 ohm resistor, which causes a current of 1 A to flow.
41
1 Ohm
The resistance of a resistor with a potential difference of 1 V across it and a current of 1 A flowing through it.
42
Ohm's Law
For a metallic conductor at constant temperature, the current through it is directly proportional to the potential difference across its ends.
43
1 Amp.
The current flowing through a resistor of 1 ohm with a potential difference of 1 V across it.
44
Kirchhoff's First Law
Based on conservation of charge, at any point in a circuit, the total current into the point is equal to the total current out of the point.
45
Kirchhoff's Second Law
Based on the conservation of energy, for any closed loop in a circuit, the sum of the EMFs is equal to the sum of the potential difference.
46
Terminal Potential Difference
The potential difference between the actual contacts pf a power supply. Given by the EMF of the supply minus the internal voltage drop.
47
Mean Drift Velocity
The average distance travelled by an electron through a circuit, per unit time.
48
1 kW-hr
An amount of electrical energy equal to 3.6 million Joules of energy.
49
Displacement (of a wave)
The distance moved, in a particular direction, from the rest point by an oscillating particle.
50
Amplitude
The maximum distance moved from the rest point.
51
Wavelength
The length for one complete cycle.
52
Period
The time taken for one complete cycle.
53
Frequency
The number of cycles per unit time.
54
Intensity
The power per unit cross-sectional area.
55
Longitudinal Wave
A wave where the oscillations of the particles or field are parallel to the direction of motion of the wave.
56
Transverse Wave
A wave where the oscillations of the particles or field are perpendicular to the direction of motion of the wave.
57
Progressive Wave/ Travelling Wave
A wave which transfers energy or information through the medium as a result of the oscillation of particles or a field.
58
Standing Wave/Frequency
A wave which does not transfer energy or information through the medium as a result of the oscillations of particles or a field.
59
Phase Difference
The amount by which two particles are out of step with each other.
60
Path Difference
The difference in distance travelled for two waves come from different sources but reaching the same point.
61
Wave Speed
The distance travelled by a wave per unit time. Given by the product of the wavelength and frequency of a wave.
62
Coherence
Two waves are coherent if the phase between them is constant in time.
63
Inteference
When two or more coherent waves of the same type overlap and their displacement sum together, changing the overall intensity.
64
The Principle of Superposition
When two waves of the same type overlap the resulting displacement is the sum of the individual displacement of the waves.
65
Constructive Interference
Waves have a phase difference of 0 degree so that the interference produces a maximum possible displacement.
66
Destructive Interference
Waves have a phase difference of 180 degrees so that the interference produces a minimum possible displacement.
67
Node
The point on a standing wave, created by destructive interference, such that there is no movement.
68
Antinode
The point on a standing wave, created by constructive interference, such that there is maximum movement.
69
Fundamental mode of vibration
The standing wave of largest wavelength that can exist.
70
Fundamental Wavelength
The highest wavelength of a standing wave that can exist.
71
Fundamental Frequency
The lowest frequency of standing wave that can exist in a system.
72
Harmonic
A standing wave which has a frequency which is a multiple of the fundamental frequency.
73
The electron-volt
The energy gained or lost by an electron when it moves through a voltage of 1 volt.
74
Work function
The smallest amount of energy needed to eject an electron from an atom.
75
Threshold frequency
The frequency below which, the photons do not have enough energy to eject an electron.
76
Newton's First Law of Motion
An object will move at constant velocity unless acted upon by an unbalanced force.
77
Newton's Second Law of Motion
The total unbalanced force on an object is directly proportional to the rate of change of momentum and the unbalanced force is in the same direction as the rate of change of momentum.
78
Newton's Third Law of Motion
For every force there is an equal but opposite force.
79
Linear Momentum
The product of the mass and velocity of an object.
80
Net Force on a Body
The rate of change of momentum.
81
Impulse
The change of momentum of an object.
| The product of the force on an object and the time over which the force acts.
82
Conservation of Linear Momentum
For an isolated system, the total linear momentum in any direction is a constant.
83
Perfectly Elastic Collisions
A collision where all of the kinetic energy is conserved.
84
Completely Inelastic Collisions
A collision where all of the kinetic energy is converted to other forms.
85
Inelastic Collision
A collision where kinetic energy is NOT conserved.
86
Radian
A unit of angle where one full circle (360 degrees) is equivalent to 2 pi radians.
87
Gravitational Field Strength
The gravitational force per unit mass.
| The gravitational flux per unit perpendicular area.
88
Gravitational Potential
The energy needed to bring a unit point mass from infinity to a given location.
89
Newton's Law of Gravitation
The force (F) between two point masses (M1 and M2), a distance d apart is given by : F = GM1M2/d^2
90
Electric Field Strength
The electric force per unit positive charge.
| The electric flux per unit perpendicular area.
91
Electric Potential
The energy needed to bring a unit point charge from infinity to a given location.
92
A Geostationary Orbit
The orbit of a satellite such that it is directly above a fixed point on the Earth.
93
Internal Energy
The sum of the total kinetic energy and potential energy of the atoms/molecules in a system.
94
Pressure
The force per unit area.
95
Absolute Zero
The temperature at which the internal energy of a system is a minimum.
96
Boyle's Law
For a system at constant temperature, the product of pressure and volume is a constant.
PV = constant.
97
1 mole
The amount of a substance such that there are 6.02*10^23 basic particles present.
98
Avogadro's Constant (NA)
6.02*10^23 - the number of particles in a system when there is 1 mole present.
99
Specific Heat Capacity
The amount of heat energy needed to raise 1 kg of a substance by 1 K.
100
Latent Heat of Fusion
The amount of heat energy needed to change 1 kg of a solid into a liquid.
101
Latent Heat of Vaporisation
The amount of heat energy needed to change 1 kg of a liquid into a gas.
102
Magnetic flux
A measure of the magnetic field strength, draw as a set of lines whose density is proportional to the field strength. Measure in Webers (Wb).
103
Magnetic Flux Density/Magnetic Field Strength
A strength of a magnetic field, given by the magnetic flux lines per unit area perpendicular to the flux lines. Measured in Tesla (T) or Wb/m^2.
104
1 Tesla
The magnetic field strength required to produce a 1 N force on a wire of 1 m length, with a 1 A current.
105
1 Weber
The number of flux lines through a 1 m^2 area in a field of strength 1 T.
106
Magnetic Flux Linkage
The product of the magnetic field strength and the number of turns in a coil.
107
Lenz's Law
The induced EMF is in such a direction as to oppose the change producing it.
108
Faraday's Law
The induced EMF has a magnitude given by the rate of change of flux linkage.
109
Capacitance
The stored charge in a capacitor per unit voltage across the plates.
110
1 Farad
The capacitance of a capacitor which stored a charge of 1 C when a voltage of 1 V is across the plates.
111
Capacitive Time Constant
The product of the capacitance of a capacitor and the resistance through which it is charging or discharging.
The time taken for a capacitor to reduce its charge to approximately 37% of its maximum value.
The time taken for a capacitor to reach approximately 63% of its maximum charge.
112
Angular Speed
The angle turned through per unit time.
113
Simple Harmonic Motion
The motion of an object such that its acceleration is directly proportional to the distance from a fixed point and the direction is always directed to the fixed point.
114
Proton Number/Atomic Number
The number of protons contained within the nucleus of an atom.
115
Neutron Number
The number of neutrons contained within the nucleus of an atom.
116
Mass Number/Nucleon Number
The number of protons and neutrons contained within the nucleus of an atom.
117
Isotope
An atom with the same number of protons in the nucleus but different number of neutrons.
118
Atomic Mass Unit
A 1/12 of the mass of the nucleus of a C-12 nucleus.
119
Radioactive Activity
The number of decays per unit time.
120
Decay Constant
The probability of an isotope decaying per unit time.
121
Conservation of Lepton Number
The total Lepton Number before a nuclear change will equal the total Lepton Number after.
122
Conservation of Baryon Number
The total Baryon Number before a nuclear change will equal the total Baryon Number after.
123
Binding Energy
The energy required to disassemble the protons and neutrons in a nucleus into their separate parts.
124
Binding Energy per Nucleon
The energy per particle, required to disassemble the protons and neutrons in a nucleus into their separate parts.
125
Half-life
The time taken for the activity of a substance to reduce to 50% of its value.
126
Electromagnetic Intensity
The electromagnetic power per unit area.
127
Ultrasound
A longitudinal wave with a frequency greater than 20k Hz.
128
Acoustic Impedance of a Medium.
The product of the density and speed of sound in the medium.
129
The Astronomical Unit
The average distance between the Earth and the Sun.
130
The Light Year
The distance light travels in a vacuum in 1 year.
131
The Parsec
The distance away an object would be to have a subtended angle of 1 second of an arc.
132
Olber's Paradox
For an infinite and uniform universe, the sky at night should be light not dark.
133
Hubble's Law
The speed of a receding galaxy is directly proportional to its distance from us.
134
The Cosmological Principle
When viewed on a sufficiently large scale, the properties of the universe are the same for all observers.
135
Critical Density
The density of the universe that will give rise to a flat spacetime.
136
Fluids
Materials that can flow or cannot support shear.
137
Upthrust
The upward force on an object due to a surrounding fluid, caused by the pressure on the bottom of the object being greater than on top.
138
Archimedes Principle
The upthrust is given by the weight of the fluid displaced.
