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AS Physics > AS Definitions and Laws > Flashcards

AS Definitions and Laws Flashcards

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1
Q

Acceleration

A

Rate of change of velocity.

Recall formula: a = Δv/Δt

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2
Q

Accuracy

A

Measurement is accurate if it is close to the true value.

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3
Q

Alpha particle

A

A helium nucleus.
Has 2 protons and 2 neutrons.
Stopped by paper.
Most ionising.

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4
Q

Amplitude

A

Maximum displacement from the equilibrium position to the crest.

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5
Q

Antinode

A

Point of maximum displacement in a stationary wave.

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6
Q

Base quantities

A 
Physical quantities that are used to define other physical quantities. 
mass
length,
time
temperature
current
amount of substance
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7
Q

Base units

A 
Units of base quantities; 
kg
m
s
K
A
mol.
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8
Q

Beta particle

A

A fast moving electron or positron.
Stopped by a few cm of aluminium.
Less ionising compared to alpha particle.

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9
Q

Centre of gravity

A

Point at which the whole weight of the body may be considered to act.

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10
Q

Coherence

A
  1. Constant phase difference between waves.

2. Waves have same frequency.

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11
Q

Constructive interference

A 
Occurs when two waves are in phase. 
Condition for constructive interference:
Path difference = n(lambda), where n = 0, 1, 2, …...  
or 
Phase difference = n x 2(pi) radians.
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12
Q

coulomb (C)

A

1 C of charge passes a point when a current of 1 A flows for 1 s.

(Recall formula: Q = It)

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13
Q

Couple

A

Two parallel forces which are equal but opposite. Their lines of action do not meet.

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14
Q

Current

A

Rate of flow of charged particle.

Recall formula: Q = It

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15
Q

Density

A

Mass per unit volume.

Recall formula: density = M/V

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16
Q

Destructive interference

A

Occurs when the two waves are out of phase.
Condition for destructive interference:
Path difference = (n + ½)lambda, where n = 0, 1, 2, ……
or
Phase difference = (n + ½)(2 x pi) radians

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17
Q

Diffraction

A

The spreading out (or bending) of waves when they pass through a gap (or when they pass the edge of an object).

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18
Q

Diffraction grating formula

A

n(lambda) = d sin (theta)

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19
Q

Diode

A

A device that allows current to flow through it in one direction only.

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20
Q

Displacement

A

Distance from a fixed point in a specified direction.

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21
Q

Ductile material

A

A material that can be drawn into a thin wire without breaking.

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22
Q

Efficiency

A

Efficiency = useful energy output/ total energy input
or
Efficiency = useful power output/ total power input

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23
Q

Elastic deformation

A

When a force is applied, the material changes its shape/ size. When the force is removed, the material returns to its original shape/ size.

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24
Q

Elastic collision

A

A collision in which momentum and kinetic energy are conserved.
Total k.e. before collision = total k.e. after collision.

In a perfectly elastic collision,
relative speed of approach = relative speed of separation.

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25
Q

Elastic limit

A

When extended beyond its elastic limit, a material will undergo plastic deformation (ie. it will not return to its original shape/ size after load is removed).

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26
Q

Elastic potential energy

A

Ability to do work due to deformation of an object. Also known as strain energy.
E = ½ Fe
or
E =

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27
Q

Electric field strength

A

Definition: force per unit positive charge.
Unit:

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28
Q

Electric field strength between parallel plates

A

Electric field is uniform between two parallel plates, ie. electric field strength is the same everywhere between the plates.
Formula: E = V/d

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29
Q

Electromotive force (e.m.f.) of a cell

A

Definition: Energy transferred by the cell in driving a unit charge round a complete circuit.

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30
Q

Electron volt (eV)

A

A unit of energy.
Definition: The energy transferred when an electron moves through a p.d. of 1 V.
1 eV = 1.60 x 10^-19 J

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31
Q

Energy

A

A measure of the stored ability of a body to do work.

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32
Q

Equilibrium

A

A body is in equilibrium if

  1. no resultant force in any direction
  2. no resultant moment about any point.
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33
Q

Force

A

Rate of change of momentum.

F =

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34
Q

Frequency

A

Number of oscillations per unit time.

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35
Q

Gamma radiation

A

Electromagnetic waves. Speed of 3.00 x 10^8 m s^-1.

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36
Q

Gravitational potential energy

A

Ability to do work due to height/position of the mass.

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37
Q

Homogeneous equation

A

Equation is homogeneous if all the terms have the same base units.

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38
Q

Impulse

A

Product of the force acting on a body and the time interval over which the force acts (ie. it is equal to the change in momentum).

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39
Q

Inelastic collision

A

A collision in which momentum is conserved but kinetic energy is not conserved.

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40
Q

Intensity of a wave

A

Power incident on a surface per unit area.

Rate of flow of energy per unit area perpendicular to the direction of the wave.

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41
Q

Interference

A

When two or more waves meet at a point, the resultant displacement is the sum of the individual displacements.

Conditions for interference:

  1. Same type of waves, ie. both transverse or both longitudinal
  2. Waves meet at a point
  3. Waves have same direction of polarisation.
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42
Q

Internal energy

A

Sum of the random distribution of the kinetic and potential energies of the particles in the substance.
K.E. of particles is proportional to temperature and P.E. of particles increases if they are further apart.

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43
Q

Isotope

A

Nuclei with the same number of protons but different number of neutrons.

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44
Q

Light-dependent resistor

A

Resistance of LDR decreases as light intensity increases.

45
Q

Limit of proportionality

A

When loaded beyond the limit of proportionality, extension will no longer be proportional to the load.

46
Q

Longitudinal wave

A

A wave in which vibrations are parallel to the direction of energy travel.

47
Q

Mass

A

A measure of a body’s inertia to changes in motion.

48
Q

Moment of a force

A

Product of force and the perpendicular distance of force from the pivot.

49
Q

Momentum

A

Product of mass and veloctiy.

50
Q

Define the newton (N)

A

1 N is the force that will give a mass of 1 kg an acceleration of 1 m s^-2.

51
Q

Node

A

A point on a stationary wave where displacement is zero.

52
Q

Nucleon number

A

The number of protons and neutrons in a nucleus. Also called mass number.

53
Q

ohm

A

Definition: The resistance between two points is 1 ohm if a current of 1 A flows when there is a p.d. of 1 V between the points.

54
Q

Path difference

A

The extra length travelled by a wave when it is compared to another wave.

55
Q

Phase difference

A

A measure of the extent to which a wave is out of phase with a reference wave.
Formula?

56
Q

Plastic deformation

A

When a force is applied, the material changes its shape/ size. When the force is removed, the material does not return to its original shape/ size.

57
Q

Potential difference

A

Definition: The p.d. between two points is the energy transferred (or work done) when unit charge moves between those points.

58
Q

Power

A

Work done per unit time.

For a body moving at constant velocity, P = Fv

59
Q

Precision

A

Measurements are precise if they are close to one another.

60
Q

Pressure

A

Force per unit area.

61
Q

Pressure in a fluid

A

p = density x g x h

62
Q

Progressive wave

A

Wave that carries energy from one point to another through vibrations within the medium.

63
Q

Proton number

A

The number of protons in a nucleus. Also called atomic number.

64
Q

Random error

A

Random errors will result in readings being scattered about the true value. Can be reduced by averaging. Example of random error: diameter of wire is not uniform.

65
Q

Resistance

A

Definition: Ratio of p.d. between the points to the current flowing between them.

66
Q

Resistivity

A

R = (resistivity x length) / cross-sectional area

67
Q

Scalar quantity

A

Quantity with magnitude only. Eg. mass, density, pressure, speed, distance.

68
Q

Semiconductor

A

For a semiconductor, resistance decreases as temperature increases. This is because the atoms in a semiconductor release electrons when temperature is higher.

69
Q

Speed

A

Distance travelled per unit time.

70
Q

Spring constant

A

Force per unit extension.

71
Q

Stationary wave (or standing wave)

A

Stationary wave is formed by superposition of two waves of same type and same frequency that are travelling in opposite directions (eg. when incident wave and reflected wave meet, they superpose). Speed of stationary wave is the speed of the incident wave.

72
Q

Strain

A

Ratio of extension to the original length. No unit.

73
Q

Stress

A

Force per unit cross-sectional area.

74
Q

Systematic error

A

Will result in constant error in all readings. It cannot be eliminated by averaging. Eg. zero error of micrometer screw gauge.

75
Q

Terminal velocity

A

Constant velocity of a falling object, when weight = air resistance + upthrust.

76
Q

Thermistor

A

A semiconductor device. Its resistance decreases as its temperature increases.

77
Q

Torque of a couple

A

Product of one force and the perpendicular distance between the two forces.

78
Q

Transverse wave

A

A wave in which vibrations are perpendicular to the direction of energy travel.

79
Q

Ultimate tensile stress

A

The maximum stress for a material.

80
Q

Upthrust

A

The vertical force exerted by a fluid on an object when it is immersed in the fluid. It is due to differences in pressure at different depths.

81
Q

Vector quantity

A

Quantity with magnitude and direction. Eg. velocity, force, momentum, acceleration

82
Q

Velocity

A

Rate of change of displacement.

83
Q

Viscous force

A

Frictional force exerted on an object as it moves through a fluid.

84
Q

volt (V)

A

Definition: The p.d. between two points is 1 V when 1 C of charge moves between those points and 1 J of energy is transferred.

V = W/Q

85
Q

Wavelength

A

Distance between two consecutive crests
or
Distance between two consecutive troughs.

86
Q

Weight

A

Gravitational force acting on a mass.

87
Q

Work

A

Product of force and distance moved in the direction of force.

W = F x d

88
Q

Work done by an expanding gas

A

Work done = pressure x change in volume

In a p-V graph, work done is the area under the graph.

89
Q

Work done in stretching a spring

A

W = ½ Fe = ½ ke^2

In a F-e graph, work done = area under graph.

90
Q

Young double slit

A

wavelength = ax/D

91
Q

Young modulus

A

Ratio of stress to strain.

E = stress/strain

92
Q

Newton’s 1st law of motion

A

A body at rest will remain at rest and a moving body will continue moving in a straight line with constant speed, unless an external resultant force acts on it.

93
Q

Newton’s 2nd law of motion

A

The resultant force is equal to the rate of change of momentum.

94
Q

Newton’s 3rd law of motion

A

If body A exerts a force on body B, then body B exerts an equal force on body A in the opposite direction. The forces are of the same type.

95
Q

Principle of conservation of momentum

A

The total momentum of a system before a collision equals to the total momentum after collision, provided that no external force acts on the system.

96
Q

Principle of moments

A

The sum of clockwise moments about any point is equal to the sum of anti-clockwise moments for a body in equilibrium.

97
Q

Hooke’s Law

A

Force is proportional to extension, provided that the limit of proportionality has not been exceeded.

98
Q

Principle of superposition

A

When two or more waves meet, the resultant displacement is the vector sum of the individual displacements of the waves.

99
Q

Ohm’s law

A

The current passing through a conductor is proportional to the potential difference across it, provided that its temperature remains constant.

100
Q

Kirchhoff’s 1st law

A

The sum of currents entering a point in a circuit is equal to the sum of currents leaving the point.

101
Q

Kirchhoff’s 2nd law

A

The sum of e.m.f.s in a closed circuit is equal to the sum of potential differences.

102
Q

Doppler effect

A

The change in the observed frequency when the source is moving relative to the observer.

103
Q

Strong nuclear force

A

The force that holds the nucleus together. It acts over very short distances (10-14 m).

104
Q

Hadrons

A

Particles that are affected by the strong nuclear force. Examples: protons and neutrons.

There are 2 types of hadron:
Baryons
Mesons

105
Q

Leptons

A

Particles that are NOT affected by the strong nuclear force.

Examples: electrons, neutrinos, positrons and antineutrinos.

106
Q

Types of quark

A

up (u)
down (d)
strange (s)

107
Q

Baryons

A

Particles that are made up of 3 quarks.

Examples: protons and neutrons.

108
Q

Fundamental particles

A

Particles that do not appear to be composed of any smaller particles.
Examples: quarks and leptons

AS Physics (3 decks)

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