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(A) Physics > A > Flashcards

A Flashcards

1
Q

What is the average speed (m/s) of walking

A

1 m/s

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2
Q

What is the average speed (m/s) of running

A

5

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3
Q

What is the average speed (m/s) of cycling

A

7

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4
Q

What is the average speed (m/s) of olympic cycling

A

20

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5
Q

What is the average speed (m/s) of a strong wind

A

13

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6
Q

What is the average speed (m/s) of a car

A

22

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7
Q

What is the average speed (m/s) of a train

A

56

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8
Q

What is the average speed (m/s) of sound

A

330

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9
Q

What is reaction time

A

The time from seeing an event and acting on it - e.g pressing a stopwatch

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10
Q

How do speed cameras work

A

They are placed 100m apart
They take a photo when you enter the zone and when you leave
Your speed is calculated using the time it took for both photos to be taken and the distance

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11
Q

Why is some equipment better than others
(Emg using a light gate over a stopwatch)

A

Some are more accurate and have a higher resolution
They also may record data to more significant figures / decimal places

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12
Q

What is one issue with older speed cameras

A

They couldn’t ensure you maintained a constant speed due to the small 10m distance
People could slow down and quickly speed up to avoid the cameras

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13
Q

What are instantaneous speed cameras

A

Speed cameras that measure speed at a single point

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14
Q

How do instantaneous speed cameras work

A

They send electromagnetic waves onto an oncoming vehicle
The camera measures the time taken for subsequent pulses of reflected light to reach the camera
The time taken between the reflected light is used to calculate distance

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15
Q

How do speedometers measure speed

A

The calculated speed from how fast the wheel is moving (rotations per second) and the wheels circumference to find distance

They then divide the distance by time

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16
Q

What is one benefit of using light gates

A

They are more effective at measuring time as they eliminate reaction time
They also have a higher resoloution

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17
Q

How can reaction time be trained

A

Studies have shown playing video games improve hand eye coordination.
They are used to improve hand eye coordination of soldiers

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18
Q

What can affect your reaction time

A

Alcohol - it is a depressant (slows nervous system)

Being distracted / tired

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19
Q

What is the ruler drop experiment used for

A

To measure reaction time.
A ruler is dropped with no stimuli by one person
Another has to catch it
A chart is used to convert the distance you caught it at to reaction time

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20
Q

What is thinking distance

A

The distance you travel before reacting to a stimulus

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21
Q

What is the breaking distance

A

Distance a car travels after the brakes on a car have been pressed

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22
Q

What factors affect thinking distance

A

The same factors that affect reaction time affect thinking distance

Alcohol / drugs
Being distracted by people / the radio / a phone

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23
Q

What is the stopping distance

A

The total distance travelled (braking distance + thinking distance)

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24
Q

What is the purpose of having speed limits

A

To ensure that cars do not crash into one another if one stops.

By going at lower speeds the stopping distance will be lower

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25
Q

What factors affect breaking distance

A

Quality of the road
Quality of the cars wheel / brakes

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26
Q

How are velocity time graphs used to calculate stopping distance

A

First section is the thinking distance
When the velocity begins to decrease that is the breaking distance

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27
Q

Why are seatbelts important

A

When wearing a seatbelt, if the car suddenly stops the belt exerts a force on you.
This force stops you from being flung forward and hitting the dashboard

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28
Q

How does the size of deceleration and the force applied during a crash relate

A

The larger (faster) the deceleration the greater the force

This can cause seatbelts to break

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29
Q

How can you calculate the force applied to a person by a seatbelt in a car crash

A

Force = mass × acceleration

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30
Q

What force do you feel if you are accelerating at twice the acceleration due to gravity

A

You experience 2gs
This is a force equal to your weight

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31
Q

Why do cars have airbags, and cars with crumples zones

A

They increase the time of collision, so the rate of deceleration is slower, this means the force applied is weaker and less damage is done to your body

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32
Q

What is the average mass of a person

A

70kg

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33
Q

What is the impulse (speeds)

A

The impulse is change in momentum and is calculated by doing force × time

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34
Q

How do you calculate acceleration

A

Change in speed ÷ time

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35
Q

What are renewable sources

A

An energy source that will not run out

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36
Q

Advantages and disadvantages of using fossil fuels

A

A:
Reliable
Power stations are cheap to maintain
Provides enough energy
Cheap to extract

D:
Slowly running out
Can cause damage to the environment (e.g.oil spillages)
Produces sulfur dioxide (causing acid rain)
Greenhouse gases

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37
Q

Advantages and disadvantages of using nuclear enegy

A

Advantages:
Reliable
Provides enough energy
Clean (no greenhouse emissions)
Not many accidents

Disadvantages
Cost to build / decommission a nuclear power plant is high
Produces nuclear waste (difficult to dispose of)
Risk of meltdown (chernobyl)

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38
Q

What energy sources are mostly used for heating

A

Fossil fuel
Biofuels
The sun (solar heating)
Water pumped into hot rock

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39
Q

What fuels do we use predominantly for transport

A

Fossil fuels
Bio fuels

40
Q

Description, advantages, disadvantages of solar energy

A

Energy transferred by light (in solar panels) is used to conduct electricity

A - no pollution, no running costs, can be used in remote areas, wont run out

D- High initial costs, need light to work, dont produce much electricity

41
Q

Description, advantages, disadvantages of wind energy

A

Blades on a turbine are pushed by wind
This causes a generator to rotate and electricity is produced

A- no pollution, low running costs, wont run out

D- Initial costs are high, appear ugly (spoil the view), only produce electricity when windy, dont produce much electricity

42
Q

Description, advantages, disadvantages of hydro-electricity

A

A dam stores GPE in water
Water is allowed to flow, turning a turbine, this turns a generator

A- no pollution, can respond rapidly to energy demands, wont run out

D - High initial costs, damages the environment and habitats in construction

43
Q

Description, advantages, disadvantages of biofuels

A

Animal waste / plant matter is burnt to produce electricity

A - reliable, carbon neutral

D- can be expensive to refine, areas destroyed for the growth of biofuels

44
Q

Description, advantages, disadvantages of tidal energy

A

A tidal barrage is built across an estuary
As the river flows in or out the turbines are turned

A- No pollution, low running costs, reliable (tides are predictable) wont run out

D- Initial costs are high, can damage the environment / alter habitats, dont constantly produce electricity

45
Q

How can other methods over fossil fuels be used for heating

A

Building houses that maximise heating by the sun
Heating water using solar water heating systems (solar panels)
Heat your house with hot water beneath the ground

46
Q

How is energy use changing

A

The use of renewable energy is on the rise however most areas still mainly use non renewables

47
Q

Why arent renewable energy sources are main sources of energy

A

They are expensive
Cant provide enough energy to meet demands
Many are unreliable (solar + wind)

48
Q

What is considered before using a specific energy source

A

Cost
Effect on environment
Contribution to climate change
How long sources will last

49
Q

Why is relying on fossil fuels bad (other than environmental impact)

A

As more are used they will become scarce.
This will cause the cost of using fossil fuels to increase

50
Q

What is the national grid

A

The power stations, underground and overland wires, pylons and transformers that supply electricity to homes in the uk

51
Q

How does voltage change throughout stages of the national grid

A

Generator produces alternating voltage at 25,000V at the power station
This is increased to nearly 400,000v as it is transported to substations
At substations the voltage is slowly decreased until hitting 230v at your home

52
Q

Why is kess energy lost to the surroundings at a higher voltage

A

Energy transferred per second of electrical working = p.d × current

When the p.d is higher the current is lower so less energy is lost to the surroundings

53
Q

Why is energy transferred at higher boltages in the national grid

A

If they were transferred at low voltages energy would be wasted and more power would be needed

This means more fossil fuels would have to be burnt

54
Q

What is the domestic supply

A

Electricity used in homes / buieness with a.c 230V and a frequency of 50hz

55
Q

What is a live wire

A

The wire in a plug that is connected to 230V
It is usually brown and located next to the fuse

56
Q

What is the neutral wire

A

A wire in a plug that has a voltage of 0v
It is often blue

It makes a complete circuit with the appliance, allowing current to flow into it

57
Q

What is the earth wire

A

A wire in a plug that is connected to the earth (metal plate under your home) which a current flows through if there is a fault

It is often green and yellow, and found at the top of the plug

It is not connected to the mains electricity

58
Q

What happens if the live wire becomes loose in an appliance

A

It can touch the metal casing causing it to be live

If you then touched the live casing a pmd of 230v would flow across you and then into the ground (as you are connected to the earth)

59
Q

How does the earth wire increase your saftey

A

If the live wire becomes loose and you touched the case instead of flowing through you the current flows through the earth wire
This is because the wire has less resistance than you

60
Q

How does insulation increase safety of plugs

A

Coating the case in plastic means the voltage will not pass through you

Double insulated plugs dont need an earth wire

61
Q

How do fuses work

A

Fuses are thin pieces if wire found in plugs
They have a low resistance, so current will easily flow through them
This causes the fuse to melt, breaking the circuit

They come in ratings of 3 5 and 13 amps
The fuses current rating is always higher than the appliances

62
Q

What is red shift

A

The increase in the wavelength of light emitted from a source that is moving away from you

63
Q

How can we tell galaxies are moving away from us

A

If the lines on an absorption spectrum are towards the red end of the spectrum (red shifted) they are moving away from us

64
Q

How can you tell if something (e.g) a galaxy is moving towards you

A

The light coming from it is blue shifted (shorter wavelength)

65
Q

What is the big bang model

A

A model of the beginning of the universe that suggests all of space and time expanded from a singular point smaller than an atom

66
Q

How does red shift support the big bang model

A

It shows that galaxies are moving away from us, and the further away it is the faster it is moving

This suggests that the universe has been expanding from a single point

67
Q

What is cosmic microwave background radiation

A

Microwave radiation that is detected in all directions

68
Q

How does cosmic background microwave radiation support the big bang theory

A

The wavelength is increasing, suggesting that the radiation has been expanding from one point
(It initially had shorter wavelength)

This means the universe must be exoanding

69
Q

What is a planet

A

A spherical object (due to gravity) that orbits a star

70
Q

What is a moon

A

An object that orbits a planet

71
Q

What is a minor planet

A

Anything that orbits the sun other than a comet or a planet

E.g dwarf planets like pluto

72
Q

What is a comet

A

An object made of ice and dust that orbits stars

73
Q

What are the ‘inner plants’ in our solar system

A

Mercury
Venus
Earth
Mars

74
Q

What are the outer plants

A

Jupiter + saturn (gas giants)
Uranus + neptune (ice giants)

75
Q

How are stars initially formed / main star sequence

A

Gas and dust spiral together forming a protostar due to gravity

Temperatures increase as particles collide together more frequently

When the temperature (and pressure) is high enough hydrogen nuclei can undergo nuclear fusion

The star then enters a star of equilibrium where the energy released in nuclear fusion results in an outward presence expanding the star
But the gravity also is pulling inwards

76
Q

What happens to low weight stars after the main star sequence

A

Hydrogen in the corr slowly runs out and the fission of heavier elements occurs

This causes the star to swell up and cool forming a red giant

When the red giant runs out of fuel it becomes stable and ejects its outer layer

The dust and gas ejected forms a planetary nebula

The hot solid core left behind is a white dwarf, which will eventually cool and fade away

77
Q

What happens to high weight stars after the main star sequence

A

When hydrogen runs out the fission of heavier elements occurs

This forms red supergiants which glow more brightly as they undergo fission

They expand and contract several times forming heavier elements

When they run out of fuel they collapse in on themselves in a massive explosion called a supernova

The supernova throws outer layers of dust and gas into space leaving a dense neutron star

If the neutron star is big enough it can form a black hole

78
Q

What are natural satellites

A

A natural object in orbit of a planet

79
Q

What is an artificial satellite

A

An artificial object that orbits a planet with a specific purpose

80
Q

What is a geostationary orbit

A

Takes 24 hours for 1 orbit (same speed as the earth)
36,000km above the earth (foxed position)

Used for communications

81
Q

What is a low polar orbit

A

2 hours for 1 orbit up to 2000km above the earths surface
Orbits around the poles

Used for observing weather patterns / spying

82
Q

What is a satellite

A

A smaller object that orbits another

83
Q

How do you calculate the gravitational force on an object in orbit

A

It is inversely proportional to r²

R is the orbital radius

84
Q

How do objects stay in orbit

A

If an object is at the correct speed it will remain in orbit

If the force of the satellite is equal to the force of gravity it will remain in orbit

The velocity of an object in orbit is always changing as its direction is always changing

85
Q

How do you calculate orbital speed

A

2πr ÷ time

R is the orbital radius and is measured from the center of the star / planet to the center of the satellite

86
Q

What type of radiation do hotter objects emit (and cooler)

A

Hotter - more radiation with a ↑frequency and ↓wavelength

Colder - more radiation with a ↓frequency and ↑ wavelength

87
Q

Why do thermal imaging cameras show red for hotter objects

A

Red is at a lower frequency and longer wavelength than blue

However due to the association of red being hot the colours are often switched

88
Q

What determines an objects temperature

A

The amount of radiation it emits and absorbs

If an object emits more radiation than it absorbs its temperature will increase

89
Q

Why does the earths temperature increase

A

It abosrbs radiation from the sun and emits radiation back into space

The earths atmosphere reflects some of the radiation back at the earth

As it absorbed more radiation than it reflects the temperature increases

90
Q

What is the earth made of

A

A solid inner cire and liquid outer core
Mantle floats on the outer core

91
Q

What are p-waves

A

Longitudinal ‘primary’ waves

92
Q

What are s waves

A

Transverse ‘ secondary waves’

They are slower than p- waves

They cannot travel through liquids

93
Q

What are seismometers

A

Tools / a machine used to detect seismic waves produced by earthquakes

94
Q

How do p-waves and s-waves prove that the earths core is liquid

A

P- waves and S-waves are predominantly located at the earthquakes center

However there are shadow regions where they cant be detected
P-waves can be found on the opposite side of the earthquake epicenter
S-waves cannot

As s-waves cant move through liquids the earths outer core must be liquid

95
Q

What does it mean if an object is in thermal equilibriumn

A

It emits and absorbs the same amount of radiation

(A) Physics (10 decks)

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