Physics Keywords Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Oscillate

A

To move to and fro about a certain position along a line (vibrate).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Angle of incidence

A

The angle between the incidence (incoming) ray and the normal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Beta radiation

A

Beta particles, high energy electrons created in, and emitted from unstable nuclei.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Boiling point

A

The temperature at which a pure substances boils or condenses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Split-ring communicator

A

Metal contacts on the coil of a direct current motor that connects the rotating coil continuously to its electrical power supply.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Alpha radiation

A

Alpha particles, each containing two protons and two neutrons, emitted by unstable nuclei. Also referred to as a helium nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Ohm’s law

A

The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Momentum

A

This equals mass (in kg) x velocity (in m/s).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Transmission

A

A wave passing through a substance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Thermal conductivity

A

The property of a material that determines the energy transfer through it by conduction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Internal energy

A

The energy of the particles within a substance due to their individual motion and positions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Nuclear fusion

A

The process where small nuclei are fused together to form a larger nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Magnification

A

The image height ÷ the object height

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Magnetic field line

A

Line in a magnetic field along which a magnetic compass points - also called a line of force.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Specific latent heat of fusion

A

The energy needed to melt 1 kg of a substance with no change of temperature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Errors

A

In readings, measurements or results. Also known as uncertainties.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Work

A

The energy transferred by a force. Work done (Joules, J) = force (Newtons, N) x distance moved in the direction of the force (metres, m)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Weight

A

The force of gravity on an object (in Newtons, N).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Compression

A

Squeezing or pressing together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

White light

A

Light that includes all the colours of the visible spectrum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Red giant

A

A star that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Longitudinal waves

A

Waves in which the vibrations are parallel to the direction of energy transfer. The wave direction is the same as the oscillations.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Step-up transformer

A

An electrical device that is used to step-up (increase) the size of an alternating potential difference.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Parallel (circuit)

A

Components connected in a circuit so that the potential difference across each is the same.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Alternating current (A.C.)

A

An electrical current in a circuit that repeatedly reverses its direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Gamma radiation

A

Electromagnetic radiation emitted from unstable nuclei in radioactive substances.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Infra-red radiation

A

Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Driving force

A

The force of a vehicle that makes it move (also called motive force or thrust).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Induced magnetism

A

Magnetisation of an unmagnetised magnetic material by placing it in a magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Generator effect

A

The production of a potential difference using a magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Inverse proportionality

A

This is where two variables are related such that making one variable n times bigger, causes the other to become n times smaller (e.g. doubling one quantity causes the other to halve).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Risk

A

The likelihood that a hazard will actually cause harm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

S-wave Secondary seismic wave

A

Transverse waves that shake the Earth from side to side as they pass through.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Count rate

A

The number of counts per second detected by a Geiger counter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Inertia

A

The tendency of an object to stay at rest or to continue in a uniform motion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Latent heat

A

The energy transferred to or from a substance when it changes its state.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Angle of reflection

A

The angle between the reflected (outgoing) ray and the normal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Atomic number

A

The number of protons (which equals the number of electrons) in an atom. Also called the proton number.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Scalar

A

A physical quantity, such as mass or energy, that has a magnitude only (unlike a vector which has magnitude and direction).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Concave (diverging) lens

A

A lens that makes parallel rays diverge (spread out).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Newton’s third law of motion

A

When two objects interact with each other, they exert equal and opposite forces on each other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Effort

A

The force applied to a device, used to raise a weight or move an object.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Nuclear fission

A

The process in which certain, large nuclei (uranium-235 and plutonium-239) are spilt into two fragments, releasing energy and two or three more neutrons as a result.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Protostar

A

The concentration of dust clouds and gas in space that forms a star.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Reflection

A

The change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Renewable energy

A

Energy from natural sources that is always being replenished so that it will never run out.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Dissipation of energy

A

The energy that is not usefully transferred or stored. Transferred to less useful forms e.g. thermal energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Earth wire

A

The wire in a mains cable used to connect the metal case of an appliance to earth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Supernova

A

The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses on to the core and rebounds.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Limit of proportionality

A

The limit for Hooke’s law applied to the extension of a stretched spring.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Redshift

A

The increase in the wavelength of electromagnetic waves emitted by a star or galaxy due to its motion away from us. The faster the speed of the star or galaxy, the greater the redshift is.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Neutrons

A

Uncharged particles of the same mass as protons. The nucleus of an atom consists of protons and neutrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Series (circuit)

A

Components connected in a circuit in such a way that the same current passes through each of them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Hooke’s law

A

The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Extension

A

The increase in length of a spring (or material) from its original length.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Motor effect

A

When a current is passed along a wire in a magnetic field, and the wire is not parallel to the lines of the magnetic field, a force is exerted on the wire by the magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Red supergiant

A

A star much more massive than our Sun that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Directly proportional

A

A graph will show direct proportionality if the line of best fit is a straight line and passes through the origin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Specular reflection

A

Reflection from a smooth surface. Each light ray is reflected in a single direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

White dwarf

A

A star that has collapsed from the red giant stage to become much smaller, hotter, and denser.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

P-wave (Primary seismic wave)

A

Longitudinal waves that push or pull on the material that they move through, as they move through the Earth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Principle of moments

A

For an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that same point.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Diode

A

A non-ohmic conductor that has a much higher resistance in one direction (its reverse direction) than in the other direction (its forward direction).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Plugs

A

A plug has an insulated case and is used to connect the cable from an appliance to a socket.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

National grid

A

The network of cables and transformers used to transfer electricity from power stations to consumers (I.e. homes, shops, offices, factories, etc.).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Physical change

A

A change in which no new substances are produced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Ionisation

A

Any process which causes atoms to become charged.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

LED (Light emitting diode)

A

A diode that emits light when it conducts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Closed system

A

An object or group of objects for which the total energy is constant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Resultant force

A

A single force that has the same effect as all the forces acting on the object.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Parallelogram of forms

A

A geometrical method used to find the resultant of two forces that do not act along the same line.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

Rarefaction

A

Stretched apart.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

Velocity

A

Speed in a given direction (in metres per second, m/s).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

LDR (Light dependent resistor)

A

A resistor whose resistance depends on the intensity of the light it is exposed to.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

Thermistor

A

A resistor whose resistance depends on the temperature of the thermistor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

CMBR (Cosmic Microwave Background Radiation)

A

Electromagnetic radiation that has been travelling through space ever since it was created shortly after the Big Bang.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

Wavelength

A

The distance from one wave crest to the next (metres, m).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Terminal velocity

A

The velocity reached by an object when the drag force on it is equal and opposite to the force making it move. e.g. Air resistance and gravity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Force multiplier

A

A lever used so that a weight or force can be moved by a smaller force.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Refraction

A

The change of direction of a light ray when it passes across a boundary between two transparent substances (including air).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Magnitude

A

The size or amount of a physical quantity.

82
Q

Reactor core

A

The thick steel vessel used to contain fuel rods, control rods and the moderator in a nuclear fission reactor.

83
Q

Neutral wire

A

The wire of a mains circuit that is earthed at the local substation, so its potential difference is close to zero.

84
Q

Power

A

The energy transformed or transferred per second. Measured in watts, W.

85
Q

Ion

A

A charged molecule or atom.

86
Q

Seismic waves

A

Shock waves that travel through the Earth and across its surface as a result of an Earthquake.

87
Q

Acceleration

A

The change in velocity per second (metres per second per second, m/s2). A change in speed AND/OR direction.

88
Q

Mass

A

The quantity of matter in an object - a measure of the difficulty of changing the motion of an object (measured in kilograms, kg)

89
Q

Oscilloscope

A

A device used to display the shape of an electrical wave.

90
Q

Contrast medium

A

An X-ray absorbing substances used to fill a body organ so that the organ can be clearly seen on a radiograph.

91
Q

Big Bang Theory

A

The theory that the Universe was created in a massive explosion (the Big Bang), and that the Universe has been expanding ever since.

92
Q

Systematic errors

A

Cause readings to be spread, a value other than the true value, due to results differing from the true value by a consistent amount each time a measurement is made.

93
Q

Freezing point

A

The temperature at which a pure substances freezes.

94
Q

Elastic

A

A material is elastic if it is able to regain its shape after it has bene squashed or stretched.

95
Q

Specific latent heat of vaporisation

A

The energy needed to boil away 1 kg of a substance with no change of the temperature.

96
Q

Centripetal force

A

The resultant force towards the centre of a circle, acting on an object moving in a circular path.

97
Q

Isotopes

A

Atoms with the same number of protons and different numbers of neutrons. This means the mass number of the isotopes will also be different.

98
Q

Kilowatt-hour (kWh)

A

The electrical energy supplied to a 1 kW (1000 W) device in 1 hour.

99
Q

Amplitude

A

The height of a wave crest, or depth of the trough of a transverse wave from the rest position (middle line). For oscillating motion, the amplitude is the maximum distance moved by the oscillating object from its rest position.

100
Q

Ultrasound wave

A

A sound wave with a frequency greater than 20,000 Hz, above the upper limit of human hearing.

101
Q

Optical fibre

A

A thin glass fibre used to transmit light signals.

102
Q

Irradiated

A

When an object has been exposed to ionising radiation.

103
Q

Vibrate

A

To oscillate (move to and fro) around a certain position.

104
Q

Electromagnet

A

An insulated wire wrapped around an iron core that becomes magnetic when there is a current in the wire.

105
Q

Nuclear fuel

A

A substance used in nuclear reactors that releases energy due to nuclear fission.

106
Q

Gradient (of a straight-line graph)

A

Change of the quantity plotted on the y-axis, divided by the change in the quantity plotted on the x-axis.

107
Q

Electromagnetic waves

A

Electric and magnetic disturbances that transfer energy from one place to another.

108
Q

Ultraviolet radiation

A

Electromagnetic waves between visible light and X-rays on the electromagnetic spectrum.

109
Q

Step-down transformer

A

An electrical device that is used to step-down (decrease) the size of an alternating potential difference.

110
Q

Moderator

A

Substances in nuclear reactor that slows down neutrons from fission reactions.

111
Q

Biofuel

A

Any fuel taken from living or recently living materials, such as animal waste.

112
Q

Three-pin plug

A

A three-pin plug has a live pin, a neutral pin, and an earth pin. Standard use in the UK.

113
Q

Spring constant

A

Force per unit extension of a spring.

114
Q

Displacement

A

Distance in a given direction. Measured in metres.

115
Q

Efficiency

A

Useful energy transferred by a device ÷ total energy transferred to the device.

116
Q

Alternator

A

An alternating current generator.

117
Q

Transformer

A

An electrical device used to change an (alternating) voltage. See also step-up and step-down transformer.

118
Q

Gravitational field strength, g

A

The force exerted by gravity on an object of mass 1kg (in Newtons per kilogram, N/kg). It is also the acceleration of freefall in metres per second per second, m/s2.

119
Q

Microwaves

A

Electromagnetic waves between infra-red radiation and radio waves in the electromagnetic spectrum.

120
Q

Frequency of an alternating current

A

The number of complete cycles an alternating current passes through each second. The unit of frequency is Hertz, Hz.

121
Q

Carrier waves

A

Waves used to carry any type of signal.

122
Q

Normal

A

A straight line through a surface or boundary, perpendicular (90°) to the surface or boundary.

123
Q

Magnetic flux density

A

A measure of the strength of the magnetic field, defined in terms of the force on a current-carrying conductor at right angles to the field lines.

124
Q

Input energy

A

The energy supplied to a device.

125
Q

Wasted energy

A

Energy that is not usefully transferred.

126
Q

Useful energy

A

Energy transferred to where it is wanted in the form that is wanted.

127
Q

Friction

A

The force opposing the relative motion of two solid surfaces in contact. Typically used to transform kinetic energy into thermal energy.

128
Q

Upthrust

A

The upward force that acts on an object either partly or fully immersed in a fluid.

129
Q

Conservation of energy

A

Conservation of energy Energy cannot be created or destroyed, only transferred to another form.

130
Q

Virtual image

A

An image, seen in a lens or mirror, from which light rays appear to come after being refracted by a lens or reflected by a mirror.

131
Q

Newton’s first law of motion

A

If the resultant force on an object is zero, the object stays at rest if it is stationary, or it keeps moving at a constant velocity (same speed and same direction).

132
Q

Melting point

A

The temperature at which a pure substances melts or freezes.

133
Q

Nucleus

A

The tiny positively charged object composed of protons and neutrons, at the centre of every atom.

134
Q

Braking distance

A

The distance travelled by a vehicle during the time it takes for its brakes to act.

135
Q

Protons

A

Positively charged particles with an equal and opposite charge to that of an electron.

136
Q

Diverging (concave) lens

A

A lens that makes parallel rays diverge (spread out).

137
Q

Magnetic field

A

The space around a magnet or a current-carrying wire.

138
Q

Real image

A

An image formed by a lens that can be projected on to a screen.

139
Q

Translucent object

A

An object that allows light to pass through, but the light is scattered or refracted.

140
Q

Resistance

A

Resistance (in ohms, Ώ) = potential difference (in volts, V) ÷ current (in amperes, A).

141
Q

Fuse

A

A fuse contains a thin wire that melts and breaks the circuit if too much current passes through it.

142
Q

Thinking distance

A

The distance travelled by a vehicle in the time it takes the driver to react.

143
Q

Radioactive contamination

A

The unwanted presence of materials containing radioactive atoms on other materials.

144
Q

Moment

A

The turning effect or force defined by the equation: moment of a force (in Newton metres, Nm) = force (in Newtons, N) x perpendicular distance from the pivot to the line of action of the force (in metres, m).

145
Q

Free body force diagram

A

A diagram that shows the forces acting on an object without any other objects or forces shown.

146
Q

Conservation of momentum

A

In a closed system, the total momentum before an event is equal to the total momentum after the event. Momentum is conserved in any collision or explosion, provided no external forces act on the objects that collide or explode.

147
Q

Magnifying glass

A

A converging lens used to magnify a small object, which must be placed between the lens and its focal point.

148
Q

Radio waves

A

Electromagnetic waves of wavelength greater than 0.10 m.

149
Q

Newton’s second law of motion

A

The acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object.

150
Q

Black hole

A

A very dense object in space that has so much mass that almost nothing, not even light, can escape from its gravitational field.

151
Q

X-rays

A

Electromagnetic waves smaller in wavelength than ultraviolet radiation, produced by X-ray tubes.

152
Q

Radiation dose

A

The amount of ionising radiation a person or object receives.

153
Q

Dynamo

A

A direct current generator.

154
Q

Chain reaction

A

Reactions in which one reaction causes further reactions, which in turn causes further reactions, etc.

155
Q

Opaque object

A

An object that light cannot pass through.

156
Q

Density

A

Mass per unit volume of a substance, e.g. kg/m3

157
Q

Echo

A

Reflection of sound that can be heard.

158
Q

Half-life

A

The average time taken for the number of nuclei of the isotope (or mass of the isotope) to decrease by half.

159
Q

Frequency of oscillating motion

A

The number of complete cycles of oscillations per second. Equal to 1 ÷ the time period. The unit of frequency is Hertz, Hz.

160
Q

Dark matter

A

Matter in a galaxy that cannot be seen. Its presence is deduced because galaxies would spin much faster if their stars were only (visible) matter.

161
Q

Main sequence

A

The main sequence is the life stage of a star during which it radiates energy because of fusion of hydrogen nuclei in its core.

162
Q

Load

A

The weight of an object raised by a device used to lift and object, or the force applied by a device when it is used to shift an object.

163
Q

Stopping distance

A

The distance travelled by the vehicle in the time it takes the driver to think and brake.

164
Q

Static electricity

A

Electric charge stored on insulated objects.

165
Q

Electromagnetic spectrum

A

The continuous spectrum of electromagnetic waves. (Radio, micro, infra-red, visible, ultra-violet, X-rays, gamma)

166
Q

Carbon neutral

A

A biofuel from a living organism that takes in as much carbon dioxide from the atmosphere as is released when the fuel is burned.

167
Q

Live wire

A

The mains wire that has a voltage which alternates between +325V and -325V in Europe.

168
Q

Convex (converging) lens

A

A lens that makes parallel rays converge (meet) at a focal point.

169
Q

Direct current (D.C.)

A

An electric current in a circuit that flows in a single direction only.

170
Q

Converging (convex) lens

A

Converging (convex) lens A lens that makes parallel rays converge (meet) at a focal point.

171
Q

Neutron star

A

The highly compressed core of a massive star that remains after a supernova explosion.

172
Q

Line of force in an electric field

A

Line along which a free positive charge moves along in an electric field.

173
Q

Transverse wave

A

A wave where the vibration is perpendicular to the direction of energy transfer. The wave direction is at 90° to the oscillations.

174
Q

Fleming’s left-hand rule

A

A rule that gives the direction of the force on a current-carrying wire in a magnetic field according to the directions of the current and magnetic field.

175
Q

Potential difference

A

A measure of the work done, or energy transferred to the lamp by each coulomb of charge that passes through it. The unit of potential difference is the volt, V.

176
Q

Electromagnetic induction

A

The process of inducing a potential difference in a wire by moving the wire so that it cuts across the lines of a magnetic field.

177
Q

Solenoid

A

A long coil of wire that produces a magnetic field in and around the coil when there is a current in the coil.

178
Q

Nuclear fission reactor

A

Reactors that release energy steadily due to the fission of suitable radioactive isotopes, such as uranium-235.

179
Q

Speed

A

The speed of an object (in metres per second, m/s) = distance moved by the object (in metres, m) ÷ time taken to move the distance travelled (in seconds, s)

180
Q

Force

A

A force (in Newtons, N) can change the motion of an object.

181
Q

Line of force

A

Line in a magnetic field along which a magnetic compass points – also called a magnetic field line.

182
Q

Mechanical wave

A

A vibration that travels through a substance.

183
Q

Geothermal

A

Energy that comes from energy released by radioactive substances deep within the Earth.

184
Q

Tangent

A

A straight line drawn to touch a point on a curve so that it has the same gradient as the curve at that point.

185
Q

Charge-Coupled Device (CCD)

A

An electrical device that creates an electronic signal from an optical image formed on the CCD’s array of pixels. E.g. in a digital camera

186
Q

Specific heat capacity

A

The energy needed to raise the temperature of 1 kg of a substance by 1°C

187
Q

Electrons

A

Tiny negatively charged particles that orbit the nucleus of an atom.

188
Q

Vector

A

A vector is a physical quantity, such as displacement or velocity, that has both magnitude and direction (unlike a scalar which has magnitude only).

189
Q

Transparent object

A

An object that transmits all the incident light that enters the object.

190
Q

Diffuse reflection

A

Reflection from a rough surface – the light rays are scattered in different directions.

191
Q

Mass number

A

The number of protons and neutrons in the nucleus of an atom. Mass = protons + neutrons

192
Q

Wave speed

A

The distance travelled per second by a wave crest or trough (metres per second, m/s).

193
Q

Pressure

A

The force per unit cross-sectional area for a force acting on a surface at right angles to the surface. The unit of pressure is the pascal (Pa), or Newtons per square metre (N/m2)

194
Q

Principal focus

A

The point where light rays parallel to the principal axis of a lens are focussed (or, in the case of diverging lenses, appear to diverge from).

195
Q

Black dwarf

A

Black dwarf A star that has faded out and gone cold.

196
Q

Activity

A

The number of unstable atoms that decay per second in a radioactive substance.

197
Q

Deceleration

A

Change of velocity per second when an object slows down (shown as negative acceleration).

198
Q

Focal length

A

The distance from the centre of a lens to the point where light rays parallel to the principal axis are focussed (or in the case of a diverging lens, appear to diverge from).

199
Q

Electric field

A

A charged object (X) creates an electric field around itself. This causes a non-contact force on any other charged object in the field.

200
Q

Boyle’s law

A

For a fixed mass of gas at a constant temperature, its pressure multiplied by its volume is constant.