A Flashcards
What is the average speed (m/s) of walking
1 m/s
What is the average speed (m/s) of running
5
What is the average speed (m/s) of cycling
7
What is the average speed (m/s) of olympic cycling
20
What is the average speed (m/s) of a strong wind
13
What is the average speed (m/s) of a car
22
What is the average speed (m/s) of a train
56
What is the average speed (m/s) of sound
330
What is reaction time
The time from seeing an event and acting on it - e.g pressing a stopwatch
How do speed cameras work
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
Why is some equipment better than others
(Emg using a light gate over a stopwatch)
Some are more accurate and have a higher resolution
They also may record data to more significant figures / decimal places
What is one issue with older speed cameras
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
What are instantaneous speed cameras
Speed cameras that measure speed at a single point
How do instantaneous speed cameras work
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
How do speedometers measure speed
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
What is one benefit of using light gates
They are more effective at measuring time as they eliminate reaction time
They also have a higher resoloution
How can reaction time be trained
Studies have shown playing video games improve hand eye coordination.
They are used to improve hand eye coordination of soldiers
What can affect your reaction time
Alcohol - it is a depressant (slows nervous system)
Being distracted / tired
What is the ruler drop experiment used for
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
What is thinking distance
The distance you travel before reacting to a stimulus
What is the breaking distance
Distance a car travels after the brakes on a car have been pressed
What factors affect thinking distance
The same factors that affect reaction time affect thinking distance
Alcohol / drugs
Being distracted by people / the radio / a phone
What is the stopping distance
The total distance travelled (braking distance + thinking distance)
What is the purpose of having speed limits
To ensure that cars do not crash into one another if one stops.
By going at lower speeds the stopping distance will be lower
What factors affect breaking distance
Quality of the road
Quality of the cars wheel / brakes
How are velocity time graphs used to calculate stopping distance
First section is the thinking distance
When the velocity begins to decrease that is the breaking distance
Why are seatbelts important
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
How does the size of deceleration and the force applied during a crash relate
The larger (faster) the deceleration the greater the force
This can cause seatbelts to break
How can you calculate the force applied to a person by a seatbelt in a car crash
Force = mass × acceleration
What force do you feel if you are accelerating at twice the acceleration due to gravity
You experience 2gs
This is a force equal to your weight
Why do cars have airbags, and cars with crumples zones
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
What is the average mass of a person
70kg
What is the impulse (speeds)
The impulse is change in momentum and is calculated by doing force × time
How do you calculate acceleration
Change in speed ÷ time
What are renewable sources
An energy source that will not run out
Advantages and disadvantages of using fossil fuels
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
Advantages and disadvantages of using nuclear enegy
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)
What energy sources are mostly used for heating
Fossil fuel
Biofuels
The sun (solar heating)
Water pumped into hot rock
What fuels do we use predominantly for transport
Fossil fuels
Bio fuels
Description, advantages, disadvantages of solar energy
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
Description, advantages, disadvantages of wind energy
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
Description, advantages, disadvantages of hydro-electricity
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
Description, advantages, disadvantages of biofuels
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
Description, advantages, disadvantages of tidal energy
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
How can other methods over fossil fuels be used for heating
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
How is energy use changing
The use of renewable energy is on the rise however most areas still mainly use non renewables
Why arent renewable energy sources are main sources of energy
They are expensive
Cant provide enough energy to meet demands
Many are unreliable (solar + wind)
What is considered before using a specific energy source
Cost
Effect on environment
Contribution to climate change
How long sources will last
Why is relying on fossil fuels bad (other than environmental impact)
As more are used they will become scarce.
This will cause the cost of using fossil fuels to increase
What is the national grid
The power stations, underground and overland wires, pylons and transformers that supply electricity to homes in the uk
How does voltage change throughout stages of the national grid
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
Why is kess energy lost to the surroundings at a higher voltage
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
Why is energy transferred at higher boltages in the national grid
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
What is the domestic supply
Electricity used in homes / buieness with a.c 230V and a frequency of 50hz
What is a live wire
The wire in a plug that is connected to 230V
It is usually brown and located next to the fuse
What is the neutral wire
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
What is the earth wire
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
What happens if the live wire becomes loose in an appliance
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)
How does the earth wire increase your saftey
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
How does insulation increase safety of plugs
Coating the case in plastic means the voltage will not pass through you
Double insulated plugs dont need an earth wire
How do fuses work
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
What is red shift
The increase in the wavelength of light emitted from a source that is moving away from you
How can we tell galaxies are moving away from us
If the lines on an absorption spectrum are towards the red end of the spectrum (red shifted) they are moving away from us
How can you tell if something (e.g) a galaxy is moving towards you
The light coming from it is blue shifted (shorter wavelength)
What is the big bang model
A model of the beginning of the universe that suggests all of space and time expanded from a singular point smaller than an atom
How does red shift support the big bang model
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
What is cosmic microwave background radiation
Microwave radiation that is detected in all directions
How does cosmic background microwave radiation support the big bang theory
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
What is a planet
A spherical object (due to gravity) that orbits a star
What is a moon
An object that orbits a planet
What is a minor planet
Anything that orbits the sun other than a comet or a planet
E.g dwarf planets like pluto
What is a comet
An object made of ice and dust that orbits stars
What are the ‘inner plants’ in our solar system
Mercury
Venus
Earth
Mars
What are the outer plants
Jupiter + saturn (gas giants)
Uranus + neptune (ice giants)
How are stars initially formed / main star sequence
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
What happens to low weight stars after the main star sequence
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
What happens to high weight stars after the main star sequence
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
What are natural satellites
A natural object in orbit of a planet
What is an artificial satellite
An artificial object that orbits a planet with a specific purpose
What is a geostationary orbit
Takes 24 hours for 1 orbit (same speed as the earth)
36,000km above the earth (foxed position)
Used for communications
What is a low polar orbit
2 hours for 1 orbit up to 2000km above the earths surface
Orbits around the poles
Used for observing weather patterns / spying
What is a satellite
A smaller object that orbits another
How do you calculate the gravitational force on an object in orbit
It is inversely proportional to r²
R is the orbital radius
How do objects stay in orbit
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
How do you calculate orbital speed
2πr ÷ time
R is the orbital radius and is measured from the center of the star / planet to the center of the satellite
What type of radiation do hotter objects emit (and cooler)
Hotter - more radiation with a ↑frequency and ↓wavelength
Colder - more radiation with a ↓frequency and ↑ wavelength
Why do thermal imaging cameras show red for hotter objects
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
What determines an objects temperature
The amount of radiation it emits and absorbs
If an object emits more radiation than it absorbs its temperature will increase
Why does the earths temperature increase
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
What is the earth made of
A solid inner cire and liquid outer core
Mantle floats on the outer core
What are p-waves
Longitudinal ‘primary’ waves
What are s waves
Transverse ‘ secondary waves’
They are slower than p- waves
They cannot travel through liquids
What are seismometers
Tools / a machine used to detect seismic waves produced by earthquakes
How do p-waves and s-waves prove that the earths core is liquid
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
What does it mean if an object is in thermal equilibriumn
It emits and absorbs the same amount of radiation
