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Physics > Physics > Flashcards

Physics Flashcards

1
Q

How do vectors interact

A

They don’t. They are completely separate and do my effect eachother

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2
Q

What does it mean if a vector triangle is close

A

Body is in equilibrium
No resultant force
No resultant moment

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3
Q

What is a moment

A

Force x perpendicular distance from the line of action of the force to the pivot

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4
Q

What is he principle of moments

A

I equilibrium the sum of the clockwise moments is equal to the sum of the anti-clockwise moments

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5
Q

Equation of a couple

A

Force of one of the forces x perpendicular distance between the two forces

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6
Q

What is couple

A

Pair of forces of equal size which act parallel in opposite directions

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7
Q

What is the centre of mass

A

Point though which a single force on the body has no turning effect

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8
Q

Why do objects topple

A

The line of action acts outside the base area which provides a turning force. There there is a resultant moment and a resultant five causing the object to fall

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9
Q

How to reduce toppling

A

Lower the centre of mass

Increase the base

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10
Q

Conditions for equilibrium

A

Resultant force = 0

No resultant moment

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11
Q

Velocity

A

Rate of change or displacement of an object per second

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12
Q

Displacement

A

Distance in a vector between start and finish

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13
Q

D - t graph for acceleration

A

Curved graph

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14
Q

D - t graph for constant v

A

Straight line graph with gradient as velocity

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15
Q

How to find v on d - t graph with acceleration

A

Use a tangent

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16
Q

V - t graph for increasing acceleration

A

Curved graph

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17
Q

Area under v-t graph

A

Displacement

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18
Q

Advantages of data logging

A

Calculate the speed multiple times a second
Precise
Accurate

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19
Q

How to calculate g

A

Measure h from bottom of the ball bearing to trapdoor
Flick switch to start timer and disconnect the electromagnet
When the trapdoor is knocked down the timer stops as the circuit breaks
Repeat

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20
Q

Problems Galileo faced

A

No accurate way of measuring time

Free fall too quick

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21
Q

How to work out projectile motion

A

Work out vertical & horizontal components of v
Use the vertical v to work out the time
Multiply by two if up and down
Speed = distance/ time using horizontal v

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22
Q

Newton’s first law of motion

A

Objects move at constant velocity or stay at rest unless acted upon by an external force

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23
Q

Newton’s second law

A

F=ma
When F is the resultant force Fnet

A = g

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24
Q

Newton’s third law

A

If object A exerts a force on object B then object B exerts and equal in magnitude but opposite in direction force on A

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25
Q

Friction

A

Resistance force acting in the opposite direction to motion

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26
Q

How is speed affected in a. Fluid

A

Drag increases as the speed increases
Resultant force in direction of motion decreases
Acceleration decreases
Until drag = weight

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27
Q

How to increase max speed

A

Increase driving force

Reduce friction

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28
Q

Skydiver graph

A
  • skydiver accelerates until air resistance equals weight
  • parachute opens which increases air resistance
  • air resistance bigger than weight
  • decelerates as his speed decreases due to air resistance
  • air resistance decreases as speed decreases
  • terminal speed when weight = resistance
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29
Q

Momentum

A

Mass x velocity

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30
Q

Principle of momentum

A

Momentum is always conserved

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31
Q

Impulse

A

Change in momentum
Force x time
mv-mu

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32
Q

Force time graph

A

Area under = impulse

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33
Q

Newtons law momentum

A

Force is the rate of change in momentum

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34
Q

Elastic collisions

A

Momentum is conserved

KE is conserved

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35
Q

Inelastic collisions

A

Momentum is conserved

KE is not conserved converted into heat

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36
Q

How to reduce force

A

Increase the impact time

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37
Q

Work done

A

= energy transferred (force x distance in direction of force)

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38
Q

FcosX

A

CosX is the angle between the the direction of force and the direction of motion

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39
Q

FD graphs

A

Area under = work done

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40
Q

Energy

A

Ability to do work

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41
Q

Power

A

Rate of energy transfer

Work done per second

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42
Q

How to improve energy efficiency

A

Insulation

Oiling

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43
Q

Density

A

Mass per unit volume

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44
Q

Hookes law

A

Extension of a stretched object is proportional to the load applied up to the limit of proportionality

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45
Q

F l graph

A

Gradient is the spring constant

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46
Q

Energy stored in spring

A

0.5FxL under the FL graph

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47
Q

Elastic limit

A

Point at which once reached the wire will not return to its original length as it has been permenantly deformed. In the plastic region

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48
Q

Elastic deformation

A

Material returns to its original length and shape when force is removed after being deformed

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49
Q

UTS

A

Ultimate tensile strength

Highest peak on graph

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50
Q

Yield point

A

Where the wire temporality weakens

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51
Q

Stiffness

A

Gradient of the line of stress strain graph

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52
Q

Strength

A

Height of the graph

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53
Q

Brittle

A

Snaps with no yield

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54
Q

Ductile

A

Draws into a wire

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55
Q

Work done my band when unloading

A

Area under unloading curve

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56
Q

Energy lost by altering bonds

A

Area between loading and unloading curbed

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57
Q

Work down when loading

A

Area under loading curve

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58
Q

Strain energy

A

Work done to deform an object

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59
Q

Current

A

Flow of charge per second C/S

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60
Q

Unit of charge

A

Coulomb

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61
Q

Potential different

A

Energy transferred per unit charge

J/C

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62
Q

Charge carriers

A

Charged particles that move through a substance

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63
Q

Ductile

A

Stretches without breaking

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64
Q

Effort

A

Force applied to a machine to make it move

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65
Q

Electromotive force

A

Amount of electrical energy per unit charge produced inside a source of electrical energy

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66
Q

Inertia

A

Resistance of an object to change of its motion

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67
Q

Internal resistance

A

Resistance inside a source of electrical energy the loss of pd per unit current in the source when current passes through

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68
Q

LDR

A

Resistance decreases with increase in light intensity

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69
Q

Limit of proportionality

A

The limit beyond which when a wire or a spring is stretched its extension is no longer proportional to the force that stretches it

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70
Q

Load

A

Force needed to be overcome by a machine when it shifts or raises an object

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71
Q

Negative temperature coefficient

A

Resistance of a semiconductor decreases when temperature increases

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72
Q

Positive temperature coefficient

A

Resistance of a metal increased when temperature increases

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73
Q

Potential difference

A

Work done or energy transferred per unit charge between two points when charge moves from one point to another’s

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74
Q

Potential divider

A

Two or more resistors in series connected to a source of pd

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75
Q

Resistance

A

Pd/current

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76
Q

Resistivity

A

Resistance per unit length x area of cross section

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77
Q

Semiconductor

A

A substance in which the number of charge carriers increases when the temperature is raised

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78
Q

Superconductor

A

A material that has no electrical resistance below a certain temperature. When current flows through there is no pd across it

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79
Q

Terminal pd

A

Potential difference across the terminals of a power supply

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80
Q

Thermistor

A

Resistor which is designed to have a resistance that changed with temperature

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81
Q

uts

A

Tensile strength needed to break a solid material

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82
Q

How many electrons passing a point per second

A

Amps / charge of an electron

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83
Q

Insulator

A

Electron are attached to an atom ad cannot move away so can’t carry charge when a voltage is supplied so there’s no current

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84
Q

Metallic conductor

A

Some electrons are delocalised and can carry charge therefore is a current when pd is supplied

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85
Q

How is resistance caused

A

Collisions between charge carriers and the material

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86
Q

Ohms law

A

The pd across a metallic conductor is proportional to the current providing the physical conditions don’t change. The resistance is constant VI graph

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87
Q

Why should no current flow through the voltmeter

A

Ammeter would not show the correct reading

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88
Q

Units of resistivity

A

Ohmic meter

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89
Q

Uses of super conductivity

A

Electromagnets as no loss of energy so high magnetic fields

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90
Q

When to use VI graph or IV

A

VI shows ohms law

IV shows effect of temperature

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91
Q

When done current flow through a diode

A

0.6V

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92
Q

Electrical energy

A

Power X time (seconds)

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93
Q

Emf equations

A

V = EMF - Ir

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94
Q

Y Intercept of V I graph

A

EMF

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95
Q

Gradient of VI graph with IR

A

Gradient = - r

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96
Q

Conversation in electrical circuits

A

Charge and energy is conserved

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97
Q

When is maximum power delivered to the laod

A

When resistance is equal to internal resistance

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98
Q

Need of a potentiometer

A

Allows values down to 0V

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99
Q

What is a wave

A

Oscillation of particles of feilds

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100
Q

What is a progressive wave

A

A wave that carries merge from one place to another without transferring material

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101
Q

Cycle

A

One completely wave

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102
Q

Displacement

A

How far the wage has moved from the equilibrium

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103
Q

Amplitude

A

Maximum displacement

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104
Q

Wavelength

A

Length of one whole wave cycle

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105
Q

Period

A

Time taken for a whole cycle (1/f)

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106
Q

Frequency

A

Number of cycles per second passing a given point

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107
Q

Phase

A

Measurement of position of a certain point along a wave cycle

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108
Q

Phase difference

A

Difference in phase of two points on a progressive wave

109
Q

Mechanical waves

A

Waves that travel through a medium by vibrations of particles

110
Q

Electromagnetic wave

A

Oscillating electric and magnetic fields without the need of a medium

111
Q

Longitudinal waves

A

Has oscillations of particles parallel to the direction of travel

112
Q

Transverse wave

A

Particles oscillate perpendicular to the direction of travel

113
Q

What waves can be polarised

A

Transverse only

114
Q

What does it mean if a wave is polarised

A

Vibrations of particles are in the same plane and the wave is transverse

115
Q

What light is unpolarised

A

White light from a filament or the sun

116
Q

When is light intensity at a minimum with filters

A

When two filters are at 90 degrees to eachother

117
Q

Why is polarisation important with signals

A

Rods must be aligned with the signals as they are polarised

118
Q

What does a high frequency mean

A

Wavelength is shorter and more frequency oscillations

119
Q

How do sunglasses work

A

Reduce glare

120
Q

Refraction

A

Change of direction of a wave when it crosses a boundary at an angle in a transparent substance where the speed changes

121
Q

Diffraction

A

Spreading out if waves after passing through a gap or round an obstacle. Narrower the gap the more spreading out

122
Q

Superposition

A

Waves meet the total displacement of a point is equal to the sum of individual displacements

123
Q

Constructive inference

A

Crest and Crest or trough and trough

nY

124
Q

Destructive interference

A

Trough and crest = node

(N+0.5) Y

125
Q

Coherent

A

Waves have the same phase difference and frequency

126
Q

Node

A

Two sets of waves are 180 degrees out of phase so they cancel

127
Q

Antinode

A

Waves are Inphase so they reinforce eachother

128
Q

Energy and Stationary waves

A

Don’t transfer energy
No energy at nodes
Max energy at anti nodes

129
Q

Frequency of stationary waves

A

All particles except nodes vibrate with the same frequency

130
Q

Amplitude of stationary waves

A

Varies from 0 at nodes to max at antinodes

131
Q

Frequency of progressive waves

A

All particles vibrate at same frequency

132
Q

Amplitude of progressive waves

A

Amplitude is the same for all particles

133
Q

Conditions for a stationary wave

A

Superpose when travelling through eachother in opposite directions with the same amplitude

134
Q

How is a stationary wage formed

A

Two waves of the same amplitude and wavelength pass through eachother in opposite directions causing superposition.
When the two waves are in phase the waves reinforce eachother causing constructive interference and an Antinode.
When the two waves are 180 out of phase they cancel eachother out causing a node and destructive interference

135
Q

After how much of a cycle are waves out of phase

A

1/4 of a cycle

136
Q

Where are pressure nodes

A

And displacement antinodes and they experience the most Changes in pressure

137
Q

Where are nodes in pipes

A

At the end of the pipes where it’s closed. Furthest away from the open ends

138
Q

When does the light bend towards the normal

A

When it goes into a more dense substance with a higher refractive index

139
Q

When does light bend away from the normal

A

When the speed increases and the light goes into a less dense substance with a lower refractive index

140
Q

What is c

A

Speed of light in a vacuum

141
Q

What changes during refraction

A

Speed and wavelength

142
Q

What is the refractive index of air

A

1

143
Q

What wavelength is refracted the most

A

Shorter wavelength ie purple light

144
Q

When does total internal reflection occur

A

Angle of incidence is bigger than the critical angle

Goes from high to low refractive index

145
Q

What is the use of cladding

A

Protect the core from scratching
Reduces light lost
Allowed a Lower refractive index

146
Q

What causes a loss in amplitude

A

Absorption of of light energy by the core causing reduced signal

147
Q

What causes pulse broadening

A

Dispersion

148
Q

Modal dispersion

A

Light rays have different angles so have different paths so some take longer to pass through the fibre due to having a longer path

149
Q

How to reduce modal dispersion

A

Use a single mode dfibre

Optical fibre repeater

150
Q

Material dispersion

A

Light consists of different wavelengths that travel at different speeds in the fibre so some wavelengths reach the end faster

151
Q

How to reduce material dispersion

A

Use monochromatic light

Optical fibre repeater

152
Q

What does pulse broadening cause

A

Overlap of signals which can confuse the signals

153
Q

When do you get most diffraction

A

When the gap is the same size as the wavelength

154
Q

What light do you need to observe a diffraction pattern

A

Monochromatic coherent light

155
Q

How does white light produce a spectra

A

Wavelengths are diffracted by different amounts

156
Q

In the double slit experience what is the point of the single slit

A

Acts as a single source of diffraction to produce coherent waves

157
Q

How do light youngs fringes form

A

Light from both slits reinforce eachother as they are in phase = constructive interference

158
Q

Is there interference with single slit

A

Yes

159
Q

What increases the width between youngs fringes

A

Increase the D
Increase wavelength
Decrease slit separation

160
Q

How does increasing the slit width S affect the central fringe

A

Decreases the amount of diffraction so decreases the size of the central fringe but increases the intensity

161
Q

How does increasing the wavelength affect the central maximum

A

Increases the amount of diffraction and the central is wider but less intense

162
Q

How to increase the accuracy of w in experiment

A

Meander across several fringes and divide my number of widths

163
Q

Wavelengths of light

A

350nm to 750nm

164
Q

Properties of laser light

A

Monochromatic
Can be concentrated as parallel waves
Coherent source

165
Q

Properties of light fringe

A

Central fringe is always white as all colours contribute
Red light is diffracted more
Blue light is diffracted less
Merging occurs

166
Q

What is a diffraction grating

A

Plate with many close parallel splits

167
Q

How find out he number of orders

A

d/Wavelength as sin 90 = 1

168
Q

Types of spectra

A

Continuous
Line emission
Line absorption

169
Q

Use of continuous light source

A

Can measure the temperature of the light source as the hotter the light the shorter the wavelength

170
Q

Use of line emission spectra

A

Gas emits specific wavelengths produce a spectrum of vertical lines which are characteristic of chemical elements

171
Q

Use of line absorption spectra

A

Continuous spectra with narrow dark lines at certain wavelength due to elements in the glowing

172
Q

Nucleon

A

Protons and neutrons in a nucleus

173
Q

Nuclide

A

Type of nucleus

174
Q

Isotope

A

Same # protons and different number of neutrons

175
Q

Specific charge

A

Charge/mass ratio

176
Q

What does the strong nuclear force do

A

Overcomes electrostatic repulsions between protons

177
Q

What is the range of the strong force

A

Attractive between 0.5-4fm
Repulsive below 0.5 fm
No force beyond 4fm

178
Q

What is the range of electrostatic force

A

Infinite

179
Q

Why do large nuclei decay

A

Opposite ends aren’t attracted as wider than 4fm

180
Q

Beta - decay

A

Neutron turns into a proton and an electron and electron Anti neutrino

181
Q

Beta + decay

A

Proton changes into a neutron and positron and electron neutrino

182
Q

Photons in lasers

A

Consist of photons of the same frequency

183
Q

Power of a laser

A

nhf where n is the number of photons each second

184
Q

Annihilation

A

Two particles collide and convert their total mass into photons

185
Q

Muon

A

Heavy electron

Negative charge

186
Q

Pion

A

+ neural or -

Heavier than a muon (rest mass)

187
Q

Kaon

A
  • neutral +
    Rest mass greater than a pion but less than a proton
    Formed by cosmic rays
188
Q

What particles are affected by the weak force

A

All particles

189
Q

What particles are affected by the strong force

A

Hadrons

190
Q

Charge of an up quark

A

+2/3

191
Q

Charge of a down quark

A

-1/3

192
Q

What forms baryons

A

3 quarks of up and down

193
Q

What forms mesons

A

1 quark and 1 antiquark

194
Q

What particles must have strange quarks

A

Kaons

195
Q

What are the force mediators

A

Gluons
Photons
Bosons

196
Q

What is a baryon

A

3 quarks that decay into protons

197
Q

What is a meson

A

Made of 1 quark and 1 antiquark which don’t decay into protons

198
Q

Rest energy of products

A

Total energy - kinetic energy

199
Q

What must be conserved in particle decay

A 
Charge 
Lepton number 
Hadron number 
Energy 
Strangeness (in strong interactions)
200
Q

What is the photoelectric effect

A

Electrons are emitted from the surface of a metal when EM radiation above certain frequencies is incident on it

201
Q

How does the photo electric effect prove that light is particles

A

Electrons do not depend on intensity only on frequency. However increasing the intensity once over the threshold frequency will increase the number of electrons emitted

202
Q

How does the photoelectric effect work

A

Photons carry energy depending on the frequency
An electron absorbs energy of the photon (hf)
If the electron has enough energy to over come the electromagnetic force (exceeding the work function) it will leave the atom (ionisation)
Any excess energy will be given to the electron as kinetic energy

203
Q

What is the work functions

A

Energy needed to remove 1 electron from the surface of the metal

204
Q

Where does the electron come from on electron capture

A

Inner she’ll electron from outside the nucleus

205
Q

What happens in electron capture

A

Inner proton turns into a neutron when interacts by the weak force with an electron causing the electron to turn into a neutrino

206
Q

When are W Bosons exchanged

A

Electromagnetic and weak force

207
Q

What force causes radioactive decay

A

Electromagnetic

208
Q

What boson is exchanged in electron capture

A

W+

209
Q

Work function

A

Minimum energy required by an electron to escape from a metal surface

210
Q

Ionisation energy

A

Minimum energy needed to remove an electron from its ground state

211
Q

Characteristics of strange particles

A

Contains a strange quark

Weak force

212
Q

How do atoms emit photons from the vapour

A

Electrons bombard atoms of vapour and give them energy
Electrons move to higher energy levels
Electrons are excited
Excited electrons move to lower energy levels losing energy by emitting photons

213
Q

How does the existence of a spectrum consisting of lines of a definite frequency support the view that atoms have discrete energy levels

A

Photos of characteristic friend us emitted from atoms of a particular elements
Because atoms have discrete energy levels
Which are associated with particular energy values

214
Q

When is strangeness not conserved

A

In a weak interaction

215
Q

Excited electron

A

Electron at a higher level than the ground state

216
Q

How do Mercury atoms become excited

A

Electrons flow through the tube
Collide with mercury atoms
Raising the electrons to a higher energy level
By transferring energy to them

217
Q

What is the purpose of coating the fluorescent tube

A

Photons from Mercury atoms are high energy photons
Photons absorbed my the powder
Powder emits photons on visible spectrum
Lower frequencies / wavelengths

218
Q

Threshold frequency

A

Below a certain frequency no electrons are emitted. Minimum frequency to overcome the work function

219
Q

Specific charge

A

Ratio of charge to mass of a nucleus

220
Q

Process of pair production.

A

Photon interacts with atom
Energy of photon used to create particle antiparticle pair
To conserve momentum photon interacts with interacting particle

221
Q

Why can’t pair production take place below a frequency

A

Energy of photon depends on frequency

Not enough energy below a certain value to provide mass of particles

222
Q

Why only photons of certain frequencies cause excitation

A

Electrons occupy discrete energy levels
Need to absorb exactly the right amount of energy to move up an energy level
Photons must have the right frequency
All energy of photon absorbed

223
Q

Forces of protons in the nuncleus

A

EM and strong force

224
Q

Why do excited atoms emit photons of characteristic frequencies

A

Atoms have discrete energy levels
When electrons change levels they lose a fixed amount of nervy
Leading to photons of discrete frequencies

225
Q

What happens to photons shortly after creation

A

Annihilate with electrons to form two photons

226
Q

Difference between hadrons and leptons

A

Quarks
Not fundamental
Strong force
Mesons and baryons

227
Q

Similarities between hadrons and quarks

A 
Rest mass 
Decay 
Weak 
Electromagnetic 
Gravitate 
Can be charged
228
Q

What interaction produced strange quarks

A

Strong

229
Q

What intervention decays strange quarks

A

Weak

230
Q

When is strangeness conserved

A

Strong interactions

231
Q

What hadron has a antiparticle identical to itself

A

Pion 0

232
Q

Why is Mercury vapour at low pressure

A

Sufficient sistance between collisions for electrons to gain enough energy for excitatione

233
Q

What does the coating in the tube do to electrons

A

Mercury emits UV
Excites atoms in coating
Coating emits EM of longer wavelengths and lower frequency
Visible light

234
Q

How does an electron act as a particle

A

Can be deflected in a magnetic fields

Collisions with atoms

235
Q

How does an electron behave like a wave

A

Diffraction

Interference

236
Q

E max frequency graph

A

Y intercept is - work function
X intercept is threshold frequency
Gradient = h

237
Q

How to work out number of photo electrons per second

A

I/e

238
Q

What is light intensity

A

Measure of the energy per second by the incident of light which is proportional to the number of photons per second as each photoelectric emits only one photon

239
Q

How to work out stopping potential

A

Charge of an electron X stopping potential = Max KE

240
Q

What is the stopping potential

A

Minimum energy needed to stop photoelectric emission

241
Q

Explanation of photoelectric effect

A 
Light is incident on metal surface 
Surface absorbed a single photon 
Gains energy (hf)
If energy is greater than work function the electron will leave the surface 
Excess energy is kinetic energy
242
Q

De Broglie hypothesis

A

Electrons are diffracted by grains of positive ions in a metal
Electrons pass metal foil and diffracted only on certain directions forming rings

243
Q

How do the rings get smaller

A

Increased speed as de Broglie wavelength gets shorter

244
Q

Why can’t longitudinal waves be polarised

A

Vibrations in same direction as energy transfer

245
Q

What is a stable isotope

A

Nuclei that do not disintegrate

246
Q

Where does gamma come from

A

Unstable nuclei

247
Q

Properties of gamma

A

No mass

No charge

248
Q

Can a muon decay into a muon anti neutrino

A

No

249
Q

How do leptons decay

A

Weak interactions

250
Q

What is a stable Baryon

A

Proton

251
Q

What is the strangeness of a strange quark

A

-1

252
Q

Why is an excited atom unstable

A

Electron leaves a vacant shell which needs to be filled

253
Q

How do emission lines occur

A

Each line due to a colour and therefore a frequency of a photon emitted when de excitation occurs

254
Q

Phenomena of waves

A 
Reflection 
Refraction 
Interference
Diffraction 
Polarisation
255
Q

Phenomenas of particles

A

Reflection
Refraction a
Photoelectric effect
Excitation

256
Q

Explaination of electron diffraction

A

Metal has regular lattice of ions
Visible light cannot get through gaps but electrons can
Would expect scattered beans of electrons
But get rings

257
Q

Where is 0 phase difference

A

On the X axis with the wave increasing

258
Q

How is force proportional momentum

A

Force is equal to the rate of change of momentum

259
Q

Newtons 3rd law and momentum

A

Force is exerted on the molecule by the wall
To change its momentum
Molecule experts an equal and opposite force on the wall

260
Q

Why does kinetic energy of emitted electrons have a max value

A

E = hf
1:1 photon electron
Recieves all energy of a photon
Energy required to remove deeper electrons

261
Q

Why is there no time delay

A

Light travels as photons

Each electron absorbs one photon

262
Q

Why does threshold frequency suggest particle like properties

A

Below = no emission
Energy less that work function.
Energy of a wave increases with intensity - not in this case
Light travels as photon s
Photons have nervy depending on frequency
No time delay

263
Q

Why does increasing the frequency have on electrons

A

Increase KE

As have more energy

264
Q

How does increasing light intensity effect electrons

A

Increase number of photelecreons per second

Increase in number of photons hitting the surface

265
Q

What is the ground state

A

Electrons in the lowest energy state

266
Q

Purpose of cladding

A

Prevents scratching
Keeps signal secure
Reduces pulse broadening

267
Q

Equation of pulleys

A

Mg-mg = (M+m) a

268
Q

Equation for finishing internal resistance from different values

A

Change in V

Change in A

Physics (4 decks)

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