Definitions Flashcards

1
Q

Young’s modulus

A

Young’s modulus is stress divided by strain

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2
Q

Work done

A

The force causing a motion multiplied by the distance travelled in the direction of the motion. (Equal to the energy transferred)

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3
Q

Stress

A

Stress is the force per unit cross-sectional area

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4
Q

Strain

A

The extension per unit length

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5
Q

Spring constant

A

The force per unit extension

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6
Q

Resistivity

A

The resistance of a wire of the material of unit length

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7
Q

Refraction

A

The change in direction of a wave at the boundary between materials, caused by the speed of the wave.

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8
Q

Power

A

The energy transferred per second

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9
Q

Diffraction

A

The spreading of a wave when it meets an obstacle into regions where it would not be seen if it only moved in straight lines

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10
Q

Potential difference (P.d.)

A

The potential difference between two points is the amount of electrical energy transferred to other forms of energy when 1 coulomb of charge flows between the two points

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11
Q

Polymeric solid

A

Made up of long chain-like molecules. No long range order between molecule’s but order within molecule’s

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12
Q

OHM’s law

A

The current flowing through a metal wire at constant temperature is directly proportional to the potential difference across it

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13
Q

Mean velocity

A

The average measured velocity over a significant amount of time.
V = x/t

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14
Q

Mean speed

A

The average measured speed over a significant amount of time.
s = d/t

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15
Q

Mean acceleration

A

The average measured acceleration over a significant amount of time. a = Δv/t

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16
Q

Hooke’s law

A

The tension in a spring or wire is directly proportional to its extension from its natural length, provided the extension is not too great

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17
Q

Electrical current

A

The rate of flow of charge

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18
Q

Crystal solid

A

Atoms are arranged in a regular array (lattice). There is no long range order

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19
Q

Brittle material

A

A material with no region of plastic deformation. Under tension, it breaks by brittle fracture, caused by crack propagation

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20
Q

Amorphous solid

A

Atoms are arranged quite randomly such that they have no long-range order but they may have short range-order

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21
Q

Transition temperature

A

The temperature at which a material when cooled, loses all its electrical resistance and becomes super-conducting

22
Q

Electro motive force (EMF)

A

The electro motive force of a source is the energy converted from some other form to electrical potential energy per coulomb of charge flowing through the source

23
Q

Snell’s law

A

At the boundary between any two given materials, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant

24
Q

Scalar

A

A quantity that has only magnitude

25
Vector
A quantity that has magnitude and direction
26
Moment
The product of force and the perpendicular distance between the line of action of the force and the pivot.
27
Newtons 1st law
If the resultant force on an object is zero then the object will either remain stationary, or if it was already moving, then it will to continue to move with uniform velocity
28
Newtons 2nd law
The rate of change of momentum of a body is directly proportional to the force applied. Which takes place in the direction of the force.
29
Newtons 3rd law
If body A exerts a force on body B, then body B exerts and equal but opposite force on body A.
30
Density
The mass per unit volume
31
Progressive Wave
Is a pattern of disturbances travelling through a medium and carrying energy with it, involving the particles of the medium oscillating about their equilibrium position. It does not involver the transfer of matter.
32
Transvers Waves
The oscillations of the particles are at right angles to the direction of travel of the wave
33
Longitudinal waves
The oscillations of the particles are in line with or parallel to the direction of travel of the wave
34
Wavelength
Is the minimum distance between two points on the wave oscillating in phase
35
Frequency
Is the number of cycles of a wave that pass a given point in one second
36
Amplitude
Is the distance from the middle of the wave to the crest or the trough, the greater the amplitude the more energy the wave is carrying
37
Speed of a wave
Is the distance travelled by the wave in one second
38
Phase
Is a term used to describe the relationship between the pattern of vibration of two points on a wave
39
Polarised wave
Is a transverse wave in which particle oscillations occur in only one of the directions at right angles to the direction of wave propagation
40
Principle of superposition
States if the waves from two sources occupy the same region then the total displacement at a point is the vector sum of the displacements of the individual waves at that point
41
Coherent
Means that there is a constant phase difference
42
Stationary Waves ...
Are produced from the superposition of two progressive waves of equal amplitude and frequency travelling in opposite directions
43
Monomode fibres
Is where the core diameter is so small that the path possible through the fibre is along its axis
44
Photon
Is a discrete packet of energy, showing both particle and wave properties
45
Electronvolt
Is the energy of an electron accelerated by a potential difference of one volt
46
Photoelectric effect
When light or ultraviolet radiation of short enough wavelength falls on a surface, electrons are emitted from the surface
47
Threshold frequency
Is the minimum frequency of a photon that will cause emission of an electron from a particular metal surface
48
Black Body
Is a body or surface which absorbs all electromagnetic radiation that falls upon it. Nothing is a better emitter of radiation at any wavelength than a black body at the same temperature
49
Conservation of Baryon Number
In any interaction between particles in a system the total baryon number in the system must not change
50
Conservation of Lepton Number
In any interaction between particles in a system the total lepton number in the system must not change