p8 Flashcards
what are some of the typical speeds in eberyday for walking, running, cyling and other transportation systems?
what are some of the typical speeds for wind, sound?
what are the magnitudes of everyday accelerations?
chnage in speed/ time
guess time as 10s, 100s, 10,000s ….
what ares some methods for measuring human reaction?
ruler falling test:
a person holds a ruler just above your hand and then drops it. The length of the ruler indicates the reeaction time
what is the typical human reaction time?
0.2 seconds
What is breaking distance
Distance the car travels when a driver applies the break.
Machine role
What is the stopping distance
Thinking distance + breaking distance
What factors affect thinking distance?
(reaction time)
🟣tiredness
🟣alcohol
🟣drugs
🟣distraction
What factors affect breaking distance?
🟣weather
🟣worn tires
🟣faulty brakes
🟣badly maintained roads
They could decrease friction , increasing distance
what other factors affect thinking distance in general?
- distracted by other people in the car
- eating or drinking
- radio or satellite navigation system
how does speed affect stopping distance?
the larger the speed the larger the breaking distance, the larger the stopping distance
what are the dangers caused by large decelerations?
- car slows down, suddenly the belt exerts a force as you are still moving forwrads, sealbelt force can cause compression injuries
- you would continue moving at high speeds, colliding with dashbaord/seats, causing injury
what forces are involved in typical situation on the road?
F=MA
include the negative signs
what are the speed, accelerations and forces involved in large accerlerations?
- typical motorway speed= 70mph
- force experienced depends of collision time
- things like air bags increase collision time, decreasing the acceleration
What are the three fossil fuels?
⚫️Coal
⛽️Gas
🛢Oil
(All very energy dense)
What are the disadvantages of fossil fuels?
They emit carbon dioxide (greenhouse gases)
They are bad for the environment
They are NON- renewable sources of energy
What is the difference between a renewable source of energy and a non -renewable
Renewable: won’t run out as it is not used up when releasing energy
Non- renewable: will run out as it is used up (takes millions of years to form)
What are some examples of renewable energy sources?
- Solar ( energy from sun light)
- Wind (energy from the wind movement)
- Geothermal (energy from the earth’s heat)
- water high up in dams (hydroelectricity)
- tidal
How do fossil fuel power plants work?
- Fossil fuel is burned
Through this chemical potential energy turns into kinetic energy - The kinetic energy from burning the coal heats up water into steam
- The steam turns the turbine because of pressure
- Turbine turns the generator on
- The generator makes electricity
What are some uses for energy sources?
What is a biofuel?
A renewable fuel that is obtained from the recent living.
Eg: methane gas from sewage, ethanol, sugars,wood.
✅carbon neutral
How are biofuels carbon neutral?
Carbon dioxide is given out when a biofuel is burned however as the plants photosynthesise they take the carbon dioxide back in
what is the difference between an energy store and an energy source?
sources: physical things that you get energy from
fuels: stores energy and must be extracted
How does electricity get sent to your homes?
Power plant —step up transformer—cables/pylons—step down transformer—home (mains/sockets)
What is the national grid?
A series of cables and pylons that transfer electrical energy generated from the power plant to homes and businesses.
What does a step up transformer do?
It increases the p.d, this decreases the current (as the power stays the same)
P=I✖️V
This minimises heat loss
How does decreasing the current decrease heat loss?
Normally when an electron hits a metal ion , it’s energy is transferred to the surroundings as heat.
Deceasing the current means that there are less electrons in the wires, therefore less hit ions and less release heat.
What does a step down transformer do?
It decreases the p.d
P= I ✖️V
This increases the current
Allowing appliances at home to run without causing problems
What problems do high p.d cause?
🟡risk of electrocution and death
⚪️ appliances need to have low p.d otherwise won’t work
What is the transformer power equation?
P=I✖️V
Power of each side of the transformer should be the same (primary circuit and secondary circuit)
(I✖️V) = (I✖️V)
What is the efficiency of a transformer?
efficiency of a transformer= power out (secondary circuits)➗power in (primary circuit)
✖️100
What is the domestic electricity supply in the UK?
230v a.c at 50Hz
What is direct current?
Electric current only flows on one direction
- provided by batteries and cells
What is alternating current?
Current which continually reverses direction.
Normally have higher p.ds
Current is alternating because p.d is alternating
Describe the live wire:
A brown wire, where current comes into the appliance
Describe the neutral wire
A blue wire, where current comes out of the appliance
Describe the earth wire
A green and yellow wire, that takes away extra electrons from the wrong place and leads them to the ground.
Is what saves YOU
Describe the fuse
A tube , next to the live wire. If current is too high then it will heat up and melt - stopping the current, before exit enters the device
It saves the APPLIANCE, and reduces the risk of fires
What is the difference between 2 core wires and 3 core wires?
2 core wires do not have an earth wire, only a live and neutral. This is because they are double insulated. 230 is such a low p.d , it cannot get through plastic
3 contain the earth wire
What is the longest pin on the plug?
The earth wire. If it is plastic, this is probably used for stability rather than a wire
What is the potential difference of a live wire in respect to the ground?
Ground =0
Live wire = 230v
=230v
What is the potential difference of a neutral wire in respect to the ground?
Ground =0
Neutral =0
=0
Why does the national grid produce alternating current?
Transformers only work with an AC
Without AC, the generators will only turn once
Why do some plugs only have two wires?
Earth wire is not needed, because the appliance has no touchable metal parts which means the plastic is a DOUBLE insulator and therefore cannot become live
What is the equation regarding the voltage and amount of coils
V input Primary coils
——— —————
V output Secondary coil
Why do transformers require an Alternating Current?
🟠The A.C produces a changing magnetic field
🟡Needed to induce voltage
why have uses of different energy ssources changed over time?
- increasing population
- use of devices that use fuels (engines, cars-use of oil)
- electricity generation
industrial revoltion (coal increase in oils)
how is potential difference generated in the national grid?
across wires
What are some dangers of live wires, even if the switch in mains circuit is open ?
The live wire may become loose inside an appliance, it can touch a metal casing. If someone touches the casing there will be a potential difference of 230v (0 you) and (230v live wire). A dangerous current could flow through you
What are some preventions for dangers to prevent current flowing through you ?
Earth wire : connects case to pole in the ground, less resistance that you, discharging the current
OR
case made of plastic and is a double insulator (no earth pin), as charge cannot flow through the double insulated case to you
what is a ‘red shift’?
when a light source is moving away from you
* wavelength increasing
* frequency decreasing
what is a ‘blue shift’?
light source moving towards us
* wavelengths decreasing
* frequnecy increasinh
the more distant a galaxy is….
speed
the faster it is moving away from us
how is the other galaxies speed evidence of an expanding universe?
becuase the more distant they are the faster they are moving away from us, suggesting that we were all together at a same point
How does CMBR provide evidence for the big bang theory?
cosmic microwave background radiation comes from all directions. suggests that the once high energy with high frequnecy has been stretched out over time, so it is now in the microwave region of the electromagnetic spectrum
what is the sun formed of?
dust and hydrogen gas drawn together by gravity
how did the formation of the sun lead to fusion reactions?
and gravity pulled the gas and dust together, the centre of the core got very hot. Eventually the particles were moving fast enough for nuclear fusion reactions to start.
gravitational attraction inwards= nuclear pressure outwards (gas expand)
during a main sequence star’s lifetime how is equlibrium maintained?
equilibrium between gravitational collapse and expansion due to the energy released during fusion.
what determines the radiaition that bodies emmit in terms of intensity and wavelength
temperature
all objects emmit electromagnetic radiation
more hot objects emmit higher frequnecy
continous range
what are the 8 planets?
inner planet: mercury, venus, earth mars
outr planet: jupiter, saturn, uranus, neptune
my very easy method just speeds up nothing
what are minor planets?
anything that is not a planet or comet that is orbiting the sun
pluto
what are the differencs between inner and outer planets?
- outer plannets all have rings and alot of moons
- inner planets are rocky and have an atmosphere (venus just has CO2, mars and mercury have very thin atmospheres)
define planets
objects that are spherical becuase of gravity in orbit around the sun
how are artificial satelites different from natural satellites?
- natural satlites : a natural object in orbit around a planet
- artificial satelites: an artificial object in orbit around a planet
for a ciruclar orbit why is the velocity is changing but speed is the same?
direction is chnaging and so velocity is changing and therfore accelerates
gravity afcts at right angle to velocity
for a ciruclar orbit why is the velocity is changing but speed is the same?
direction is chnaging and so velocity is changing and therfore accelerates
gravity afcts at right angle to velocity
what happens if the speed changes for a constant orbit?
- more speed, orbit would fly off speed>force of gravity
- less speed, orbit would accelerate towards the sun
speed<force of gravity
how does the radius of an orbit correlate to the speed?
larger radius= weaker gravitational force and so less force/speed is required
what does the temperature of a body correlate to ?
- hotter= more radiation absorbed than emitted
- colder = more radiation emmited that absorbed
- constant= emits the same as absorbs
what does the temperature of the earth depend on?
the concentration of greenhouse gases in the atmosphere
as they iradiated some of the earth’s infrared back towards the earth
describe the two sesmic waves
- P waves: longitudinal , travel through solids and liquid, travel faster
- S waves: transverse travel through solids only
How do we know light is red shifted ?
Black lines correspond to the specific wavelengths of light absorbed by certain atoms in the star (since all stars contain hydrogen and helium. All spectra from stars contain a series of very specific black lines, which shift towards longer wavelengths implying light has undergone a Doppler shift.
How does CMBR provide evidence for the Big Bang
Cosmic microwave background radiation,
At the beginning all energy in universe would have had very Short wavelength gamma wavelengths. As the universe expanded, this gamma radiation would have streckten out into longer wavelengths….. currently microwaves.
as CMBR is evenly distributed across the universe , Suggest that they all started off from a single point
What is the definition of the big bag ?
A theory that takes all the energy and mass of the universe was contained within a single point in space (no volume ) which meant that it had infinite density. Then all the universe started expanding very rapidly.
What is the composition of the solar system?
How did the sun and the solar system form?
Formed from the remains of a supernova
Clouds and dust were pulled together by the force of gravity. When enough gas and dust has gathered and became dense enough to start nuclear fusion, a protostar formed. The protostar becomes denser and hotter, particles gain kinetic energy and collide allowing nuclear fusion to begin, forming a main sequencing star
What are the two overall forces adding upon a star/planet?
What is the life cycle of a star?
Describe the life cycle of a small mass star
1) dust and clouds formulate, with a gravitational pull to form a protostar
2) when protostar is dense enough to do nuclear fusion, it becomes a main sequencing star (equilibrium ) - does nuclear fusion
3) as hydrogen nuclei run out , it was collapse under graviational pressure, causing it to be more hot and dense allowing it to start the fusion for heavier elemnets, which allow it to expand into a red giant
4) the nuclei for fusion will eventually run out, reducing the radiation pressure, causing the planned to collapse into smaller planet. However since the volume of the planet has decreased the temperature increases leaving a white dwarf planet.
5) once the white dwarf cools, it becomes a black dwarf
Describe the life cycle of a larger mass star
1) the dust and air form a protostar under gravity
2) when the protostar becomes dense enough for nuclear fusion, it then becomes a main sequencing star (equilibrium)
3) helium hydrogen for fusion run out, the star collapses due to gravitational presssure, it becomes hoter and then starts the fusion of heavier elements causing it to expand to be a red super giant
4) the heavier nuclei fused together release alot of energy, resulting in a further increased Radiation pressure, enough for the explode into a supernova
5) from this super nova a neutron start is made, if it is dense enough then it is known as a black hole.
What is temperature?
The measure of the average kinetic energy of particles of a system
What happens to the particles when there is a greater temperature ?
More kinetic energy,
The faster the particles will displace, rotate and vibrate
What happens when charged particles vibrate?
The emit EM waves
What happens if the temperature of charged particles increases?
They vibrate faster, emitting a higher frequency of EM radiation
So blue bodies are hotter than red bodies
Graph of frequency and intensity of radiation at each frequency
(Increases intensity for all wavelengths)
Describe the Earth’s structure
A liquid outer core, able to do so because of pressure
How to p waves and S waves travel through the Earth?
What a geostationary orbit ?
🔵A satellite that orbits the earth every 24 hours. 🔵Launched at the equator, appears to stay in the same position give the earth’s surface (rotation is parallel to earth’s )
🔵In the horizontal plane
Eg: communication , GPS
What is a low polar orbit ?
🔵rotation is perpendicular to earth’s orbit, can can the surface of the earth very quickly
Eg: weather satellites
Describe the forces acting upon a satellite
What is a stable orbit
Maintains a constant radius about the body it is orbiting
Why do geostationary satellites have to be launched at the equator?
Ensures that the satellite’s plane of orbit, matches the plane of rotation of the earth allowing it to maintain a fixed position relative to the earth.
why have uses of different energy ssources changed over time?
- increasing population
- use of devices that use fuels (engines, cars-use of oil)
- electricity generation
industrial revoltion (coal increase in oils)
how is potential difference generated in the national grid?
across wires
What are some dangers of live wires, even if the switch in mains circuit is open ?
The live wire may become loose inside an appliance, it can touch a metal casing. If someone touches the casing there will be a potential difference of 230v (0 you) and (230v live wire). A dangerous current could flow through you
What are some preventions for dangers to prevent current flowing through you ?
Earth wire : connects case to pole in the ground, less resistance that you, discharging the current
OR
case made of plastic and is a double insulator (no earth pin), as charge cannot flow through the double insulated case to you
compare the geo stationary and polar orbits
Why are orbits circular ?
The resultant force (gravitational force) always acts perpendicular to direction of velocity. This force changes the direction of motion, so that it accelerating even though speed doesn’t change.
what must be considered when deciding which energy source must be chosen?
- cost
- effect on enviroment
- contribution to climate change
- how long the sources will last
