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Physixs > P8- Global Challenges > Flashcards

P8- Global Challenges Flashcards

1
Q

How do you convert mph to kmph?

A

Multiply by 8, divide by 5

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2
Q

How do you convert kmph to m/s?

A

Divide by 3.6

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3
Q

How do you convert mph to m/s?

A

Multiply by 4, divide by 9

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4
Q

What does each letter stand for in SUVAT?

A 
S = Displacement (m)
U = Initial velocity (m/s)
V = Final velocity (m/s)
A = Acceleration (m/s²)
T = Time (s)
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5
Q

How do you find final velocity, using initial velocity, acceleration and time?

A

V = U + AT

Final velocity = Initial velocity + (Acceleration * Time)

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6
Q

How do you find displacement, using initial velocity, time and acceleration?

A

S = UT + 1/2(AT²)

Displacement = (Initial velocity * Time) + 1/2(Acceleration * Time²)

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7
Q

How do you find final velocity² using initial velocity, acceleration and displacement?

A

V² = U² + 2AS

Final velocity² = Initial velocity² + 2(Acceleration * Displacement)
How do you find final velocity² using initial velocity, acceleration and displacement?

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8
Q

How do you find displacement using initial velocity, final velocity and time?

A

S = (U+V)/2 * T

Displacement = (Initial velocity + Final velocity)/2 * Time

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9
Q

What are typical speeds for walking, running and cycling?

A

Walking - 1.4 m/s
Running - 3 m/s
Cycling - 5.5 m/s

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10
Q

What are typical speeds for cars in a built up area, cars on a motorway and trains?

A

Cars in a built up area - 13 m/s
Cars on a motorway - 31 m/s
Trains - up to 55 m/s

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11
Q

What are typical speeds for a breeze and a gale?

A

Breeze - 5 m/s

Gale - 20 m/s

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12
Q

What is the speed of sound in air?

A

340 m/s

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13
Q

Why are large decelerations of objects and people dangerous?

A

Large declerations of objects and people (eg. in a car crash) and the forces involved can cause injuries.
This is because a large deceleration requires a large force.

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14
Q

How can you lower the force on an object so that it is less dangerous?

A

You can lower the force by slowing the object down over a longer time, ie. decreasing its deceleration.

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15
Q

How are safety features designed in cars?

A

To increase collision times, which reduces deceleration and forces, and so reduces the risk of injury.

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16
Q

Name examples of safety features in cars.

A

Seat belts stretch slightly and air bags slow you down gradually.
Crumple zones are areas at the front and back of a car which crumple easily in a collision, increasing the time taken to stop.

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17
Q

What are the two parts of the stopping distance of a car?

A

Thinking distance and breaking sistance

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18
Q

What is thinking distance?

A

The thinking distance is the distance the car travels in the driver’s reaction time (the time between noticing a hazard and applying the breaks)

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19
Q

What two factors affect thinking distance?

A

Reaction time - affected by tiredness, alcohol, drugs and distractions.
Speed - the faster you’re going, the further you’ll travel during reaction.

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20
Q

What is braking distance?

A

The distance taken to stop once the breaks have been applied.

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21
Q

What factors affect braking distance?

A

Speed
Mass of the car
Condition of the breaks
How good the grip of the tyres is

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22
Q

When testing reaction times with the ruler test, what equation can be used to find the reaction time?

A

Distance travelled by ruler ÷ (0.5 * 10 m/s²) = Time²

Square root of Time² = reaction time

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23
Q

What is the relationship between speed and thinking distance?

A

As speed increases, thinking distance increases at the same rate. This is because the higher the speed, the further you go in that time.

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24
Q

What is the relationship between speed and breaking distance?

A

They have a squared relationship - if speed is multiplied by 2, braking distance increases by 2².

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25
Q

What is the relationship between energy in the car’s kinetic energy store and work done by the brakes?

A

Energy in the car’s KE store = Work done by brakes

0.5 * Mass of car * Speed of car² = Force * Distance

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26
Q

What are typical weights of cars, buses and lorrys?

A

Car - 1000 kg
Bus - 10000 kg
Loaded lorry - 30000 kg

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27
Q

How is thinking distance and braking distance shown on a velocity-time graph?

A

Thinking distance - flat section

Braking distance - decreasing/decelerating section

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28
Q

Where does most of our energy come from?

A

Non renewable sources - sources that will one day run out. They also damage the environment.

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29
Q

What are the main non-renewable energy sources?

A

The 3 fossil fuels (coal, oil and natural gas) and nuclear fuels (uranium and plutonium)

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30
Q

How is electricity generated from burning fossil fuels in power stations?

A

As the fossil fuel burns, the oxygen in its chemical energy store is transferred to the thermal energy store of the water.
The water boils to form steam, which turns a turbine, transferring energy to the KE store of the turbine.
As the turbine revolves, so does the generator.
The generator transfers the energy electrically away from the power station.

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31
Q

How does a nuclear reactor work?

A

Similarly to a power station, but it uses the energy from nuclear fission to heat water to make steam.. etc.

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32
Q

Which is the fastest and slowest power station to start up?

A

Slowest - nuclear

Fastest - natural gas

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33
Q

What do all 3 fossil fuels release that damages the environment?

A

Carbon dioxide - coal releases the most, then oil, then natural gas. The carbon dioxide contributes to climate change and global warming.

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34
Q

What does burning coal and oil release that damages the environment?

A

Sulfur dioxide, which causes acid rain.

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35
Q

How does coal mining negatively affect the environment?

A

It ruins landscapes.

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36
Q

How can harvesting oil lead to environmental problems?

A

Oil spillages can cause huge environmental issues.

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37
Q

How can nuclear power lead to environmental problems?

A

Nuclear waste is dangerous and difficult to dispose.

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38
Q

What is a renewable energy source?

A

An energy source that will never run out. They do some damage to the environment, but nowhere near as much as non-renewables.

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39
Q

What are examples of renewable sources?

A

Biofuels, wind power, the Sun, hydro-electricity and the tides

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40
Q

What are the problems with renewable sources?

A

They don’t provide as much energy as non-renewables and the weather dependent ones can be unreliable

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41
Q

What are biofuels and why are they renewable?

A

They can be made from anything from farm waste, animal dropping and landfill rubbish to specially grown crops. They’re renewable because we can just grow more.

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42
Q

How are biofuels used?

A

They are burnt to produce electricity or to run cars in the same way as fossil fuels.

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43
Q

Biofuels are carbon neutral - what does this mean?

A

Biofuels are said to be carbon neutral because the carbon dioxide used by the plants that make the fuels during photosynthesis is equal to the carbon dioxide that is released when the fuel is burned.

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44
Q

What are the problems with biofuels?

A

In some places, large areas of land have been cleared to grow biofuel, resulting in species losing their habitats.

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45
Q

How does a wind turbine work?

A

Each turbine has a generator inside - the rotating blades turn the generator and produce electricity.

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46
Q

How much pollution do wind turbines produce?

A

None - except for a small amount when they’re manufactured.

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47
Q

What are the problems with wind power?

A

They only work when it’s windy, so you can’t always supply electricity or respond to high demand.

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48
Q

How do solar cells work?

A

They are made from special materials that release electrons when light falls on them, producing an electric current.

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49
Q

How much pollution do solar cells produce?

A

None, although they require a lot of energy to make.

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50
Q

What are problems with solar power?

A

You can’t make solar power at night or increase production when there’s high demand.

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51
Q

What is involved in producing hydro-electricity?

A

Flooding a valley by building a big dam. Rainwater is caught and allowed out through turbines.

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52
Q

Why is there a big impact on the environment from hydro-electricity?

A

The flooding of the valley has an impact on the environment as it can cause the loss of habitat for some species.

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53
Q

What is the advantage of hydro-electricity?

A

There can be an immediate response to increased electricity demand - more water can be let out through the turbines to generate more electricity.

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54
Q

What are tidal barrages?

A

Big dams built across river estuaries with turbines in them. As the tide comes in, it fills up the estuary. The water is then let out through turbines at a set speed.

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55
Q

What is an estuary?

A

The tidal mouth of a large river - where the tide meets the stream

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56
Q

What are the disadvantages of tidal barrages?

A

Although they produce no pollution, they affect boat access, can spoil the view and alter the habitat for wildlife.

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57
Q

How reliable are tidal barrages?

A

The tides are reliable - they always happen twice a day. However, their height is variable and they don’t work when the water level is the same either side.

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58
Q

What happened to the energy use in the UK in the 20th century?

A

It massively increased, as the population got bigger and people began to use electricity for more and more things. Most of this was generated using fossil fuels and nuclear power.

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59
Q

How much of the UK’s energy is from renewable sources?

A

Roughly 20% - most of our electricity still comes from coal and gas. This is partly because most renewable sources generate less electricity, and also because the weather-dependent methods fluctuate a lot.

60
Q

What has happened to the use of energy since the beginning of the 21st century?

A

It has been decreasing (slowly), as we get better at making appliances more efficient and people become aware that they need to save energy.

61
Q

How is an alternating current produced?

A

By an alternating voltage - the voltage and current both constantly change direction.

62
Q

What is the UK mains electricity?

A

Alternating current, at 50 HZ and roughly 230V

63
Q

What can you get direct current from?

A

Batteries

64
Q

What does a cathode ray oscilloscope show?

A

The height at any point shows the input voltage at that point.

65
Q

What does AC look like on a CRO?

A

A wave - going up and down in a regular pattern

66
Q

What does DC look like on a CRO?

A

A horizontal line - it doesn’t vary

67
Q

What is the national grid?

A

A network of wires and transformers that connects UK power stations to consumers. It transfers energy electrically from power stations to where it’s needed in homes and industry.

68
Q

What do you need to transmit the huge of power needed to supply the demand in the UK?

A

A high voltage or high current, as Power = Current * Voltage

69
Q

What is the problem with using high current for the National Grid?

A

With a high current, you lose loads of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings.

70
Q

Why is using voltage better for the National Grid?

A

It’s much cheaper to increase the voltage to a really high amount (to 400000V), and keep the current very low. This makes the National Grid an efficient way of transferring energy.

71
Q

How does the National Grid get voltages of 400000?

A

Transformers, all of which have two coils, the primary and secondary, joined with an iron core.

72
Q

What does the step-up transformer do in the National Grid?

A

The voltage is increased using a step-up transformer. They have more turns on the secondary coil than the primary coil.

73
Q

What does the step-down transformer do in the national grid?

A

The high voltage is reduced at the local consumer end by using a step-down transformer. They have more turns on the primary coil than the secondary.

74
Q

What is the equation that links the voltage and current in the primary coil, and the voltage and current in the secondary coil?

A

Voltage across primary coil * Current in primary coil = Voltage across primary coil * Current in secondary coil

75
Q

What are the three wires in plugs?

A

The live wire, the neutral wire and the earth wire

76
Q

What colour is the neutral wire in a plug?

A

It is the blue wire.

77
Q

What colour is the live wire in a plug?

A

It is the brown wire.

78
Q

What colour is the earth wire in a plug?

A

It is the green and yellow wire.

79
Q

What is the neutral wire for in a plug?

A

It completes the circuit - when the appliance is operating normally, current flows through the live and neutral wire. It is around 0V.

80
Q

What is the live wire for in a plug?

A

The live wire carries the voltage. It alternates between a high positive and negative voltage of about 230V.

81
Q

What is the earth wire for in a plug?

A

The earth wire is for safety. It carries the current away if something goes wrong. It’s at 0V.

82
Q

What is the voltage between the live and neutral wire?

A

The voltage between the live and neutral wire equals the supply voltage (230V for the mains).

83
Q

What is the voltage between the live and earth wire?

A

The voltage between the live and earth wire equals the supply voltage (230V for the mains).

84
Q

What is the voltage between the earth and neutral wire?

A

There is no voltage as they’re both at 0V.

85
Q

Your body is at 0V - what would happen if you touched the live wire?

A

If you touched the live wire, there’d be a large voltage across your body and a current would flow through you. This large electric shock could injure or even kill you.

86
Q

Why is there still a danger of electric shock when a plug is off?

A

Although no current is flowing, there is still a voltage in the live part of the socket, so your body could provide a link between the supply and the earth if you make contact.

87
Q

What does electricity flow through?

A

Anything that conducts. So if the live wire accidentally connects with something metal, current will flow. This could cause electric shocks and fires.

88
Q

What does it mean if something is “earthed” for safety?

A

All appliances with metal cases must be earthed for safety, meaning that the case must be attached to an earth wire.

89
Q

What happens if a fault develops in an appliance so that the live wire touches the metal case?

A

A current will flow down the earth wire.

90
Q

Why is the earth wire very thick?

A

To give it a low resistance. This means the total resistance of the circuit decreases. Current = Voltage ÷ Resistance, so this caused a big current to flow through the live wire, the case and the earth wire.

91
Q

How does the surge in current affect the fuse?

A

It melts the fuse, breaking the circuit and cutting off the live supply. This isolates the appliance, so it’s impossible to get an electric shock from the case. It also prevents fires.

92
Q

What protects your appliances getting “fried” from a current sruge?

A

Fuses and earthing

93
Q

Why does something with non-conductive casing not need an earth wire?

A

If the appliance has a non-conductive casing, then it’s double insulated. Anything with double insulation doesn’t need an earth wire as it can’t become live.

94
Q

The Solar System is made up of sun and the things orbiting it. What is including in these things?

A

Artificial satellites

95
Q

Describe planets

A

The planets of our Solar System in order from the Sun outwards - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

96
Q

Describe minor-planets

A

Planet-like objects that orbit stars, but don’t meet the rules for a planet.

97
Q

Describe natural satellites

A

eg. Moons. Smaller things orbiting planets.

98
Q

Describe artificial satelites

A

Man-made objects with specially designed orbits.

99
Q

What are satellites in geostationary orbit?

A

This means that they stay above the same point on the Earth’s surface, as the Earth rotates with them.

100
Q

What is a synonym of geostationary?

A

Geosynchronous

101
Q

What are satellites in geostationary orbit ideal for?

A

Communications (eg. TV, radio) because they stay at the same point above earth and so it is easy to point transmitters/receivers at them. They are able to transfer signals from one side of Earth to another in a fraction of a second.

102
Q

What are satellites in polar orbit?

A

They’re much closer to the Earth than geostationary satellites and so move much faster (1 orbit = less than 2 hrs)

103
Q

What do the short orbits of satellites in polar orbit mean?

A

They can scan the next part of the globe each orbit, allowing the whole surface of the Earth to be monitored each day.

104
Q

What are satellites in polar orbit used for?

A

Weather, mapping and surveilance

105
Q

What shape is the orbits of planets around the Sun and satellites around planets?

A

Almost circular. If an object is travelling in a circle, it’s constantly changing direction. This means its velocity constantly changes, so it’s accelerating.

106
Q

Because objects in orbit are accelerating, what does it mean?

A

There must be a force acting on it. For an object moving in a circle, this force is directed towards the centre of the circle and is called the centripetal force.

107
Q

What is the centripetal force on orbiting objects?

A

Gravity. It would cause the object to just fall towards whatever it is orbiting, but because the object is already moving, it just causes it to change its direction.

108
Q

How does an orbiting object stay in a circle?

A

The object keeps accelerating towards whatever it’s orbiting but its velocity at any given moment is always at right angles to this acceleration.

109
Q

What does an orbiting object need to do to orbit stably?

A

Be moving at just the right speed - too fast and it’s fly off into space, too slowly and it’d crash into whatever it’s orbiting.

110
Q

What happens to the orbit of an object the closer it gets to a planet?

A

The stronger the force, the faster the orbiting object needs to be going to avoid falling.

111
Q

What happens to an object in stable orbit if its speed changes?

A

If the object moves slower, the radius gets bigger.

112
Q

Explain the dark lines in the EM spectrum

A

Each element produces a specific pattern of dark lines at the frequencies that it absorbs.

113
Q

What is odd about the light from distant galaxies?

A

When we look at light from distant galaxies, we see the patterns of dark lines but at slightly lower frequencies (longer wavelengths) than expected.

114
Q

What is red-shift?

A

An observed increase in the wavelength of light coming from the galaxies - the light is shifted towards the red end of the spectrum.

115
Q

How does red-shift prove that galaxies are moving away from us and each other?

A

Measurements of red-shift suggest that all distant galaxies are moving away from us and each other very quickly.

116
Q

What is the red-shift like in more distant galaxies?

A

This means that further away galaxies are moving away faster than near ones.

117
Q

What is the Cosmic Microwave Background Radiation?

A

Scientists can detect low frequency microwave radiation coming from all directions and all parts of the universe. This is CMBR.

118
Q

What is Cosmic Microwave Background Radiation evidence of?

A

The Big Bang

119
Q

How is Cosmic Microwave Background Radiation proof for the expansion of the universe?

A

As the universe expands and cools, CMBR “cools” and drops in frequency.

120
Q

What was the Big Bang?

A

Space started expanding, and this expansion still continues.

121
Q

What is CMBR in relation to the Big Bang Model?

A

The left over energy from the Big Bang explosion

122
Q

What do stars initially form from?

A

Clouds of dust and gas.

123
Q

What happens to the initial form of stars (clouds of dust and gas)?

A

The temperature rises as the star gets denser and the particles collide with each other more often and with more force.

124
Q

What happens to a protostar when the temeprature gets high enough?

A

Hydrogen nuclei undergo nuclear fusion to form helium nuclei. This gives out massive amounts of energy - a star is born.

125
Q

What happens after a star is born?

A

It immediately enters a period of equilibrium - the energy released by nuclear fusion results in an outward pressure that tries to expand the star, but this is balanced by the force due to gravity (gravitational collapse).

126
Q

How long is the period of equilibrium and what is it called?

A

In this stable period, the star is called a main sequence star and it typically lasts several billion years.

127
Q

What eventually happens to the hydrogen in a main sequence star?

A

Small-to-medium sized stars like our Sun are called red giants at this stage.

128
Q

What is a red supergiant?

A

Like a red giant, but originating from a bigger star. They begin to glow brightly again as they undergo more fusion and expand and contract several times, forming even heavier elements in various nuclear reactions.

129
Q

What happens when a red giant runs out of fuel?

A

It becomes unstable and ejects its outer layer of dust and gas as a planetary nebula.

130
Q

What is the remains of a red giant after the planetary nebula is ejected?

A

A hot, dense solid core is left behind - a white dwarf, which cools down and eventually fades away.

131
Q

What happens when a red supergiant runs out of fuel?

A

They collapse in on themselves in a massive explosion known as a supernova.

132
Q

What happens when a supernova occurs?

A

It throws the layers of dust and gas into space, leaving a very dense core behind known as a neutron star. If this star is big enough, it becomes a black hole - a super dense point ins pace that not even light can escape.

133
Q

What do all objects emit?

A

Electromagnetic radiation - this covers a range of energy values, wavelengths and frequencies

134
Q

What is intensity?

A

Power per unit area

135
Q

What happens to the intensity of an object as its temperature increases?

A

As the temperature of an object increases, the intensity of every emitted wavelength increases.

136
Q

What is the relationship between intensity and wavelengths?

A

Intensity increases more for shorter wavelengths than longer wavelengths.

137
Q

How does intensity affect the peak wavelength?

A

An increase in intensity causes the peak wavelength (the most common) to decrease

138
Q

What happens to the peak wavelength of an object as its temperature increases?

A

The peak wavelength gets shorter and the intensity-wavelength distribution gets less symmetrical.

139
Q

What happens to an object that’s hotter than its surroundings?

A

It emits more radiation than it absorbs. So over time, it cools down.

140
Q

What happens to an object that’s cooler than its surroundings?

A

It absorbs more radiation than it emits. So over time, it warms up.

141
Q

What does the sun emit?

A

A spectrum of EM radiation

142
Q

What does the overall temperature of Earth depend on?

A

During night, less radiation is absorbed than emitted.

143
Q

How does sonar work?

A

By timing how long the reflected waves take to return, the distance to the seabed/an object can be calculated.

144
Q

What are the two type of seismic waves?

A

P Waves and S Waves

145
Q

What are the properties of P Waves?

A

They are longitudinal waves that travel through liquids and solids. They’re faster than S waves.

146
Q

What are the properties of S Waves?

A

They are transverse waves that only travel in solids. They travel slower than P WAVES.

Physixs (8 decks)

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