Nov + Mar PPEs Flashcards
chapters: 1 - 6, 8 - 14 & 16
What is the conservation of energy and what is energy measured in?
Energy cannot be created or destroyed - measured in Joules.
Name 6 energy stores.
- Kinetic energy
- Gravitational potential energy
- Elastic potential energy
- Thermal energy
- Chemical potential energy
- Sound energy
(sound and chemical are less relevant)
What is the equation for kinetic energy?
Ek(J) = 0.5*mass(kg)*velocity(m/s)2
What is the equation for gravitational potential energy?
Ep(J) = mass(kg)*gravitational field strength(N/kg)*height(m)
What is the equation for elastic potential energy?
Ee(J) = 0.5*spring constant(N/m)*extension(m)2
What is the equation for thermal energy?
△thermal energy(J) = mass(kg)*specific heat capacity (J/kg°C)*△temperature(°C)
In closed systems, is energy gained, lost or sustained?
Sustained, as it transfers from one store to another.
In open systems, is energy gained, lost or sustained?
Gained or lost. Typically lost to surroundings, e.g. work done against air resistance, etc.
Describe the practical to find the Specific Heat Capacity of water.
- Place the beaker on a balance and press zero.
- Add oil to the beaker and record mass of oil.
- Place a thermometer and an immersion heater into the oil. Read starting temp of oil.
- Wrap the beaker in insulating foam to reduce the thermal energy transfer to the surroundings.
- Connect a joulemeter (and a power pack) to the immersion heater you place in earlier.
- Leave oil for 30 minutes.
- Read the number of joules of energy that passed into the immersion heater and the final temperature of the oil.
Now you have all the info needed to calculate the SHC. Use the thermal energy equation (rearranged).
What is power?
The rate of energy transferred measured in watts.
How do you calculate power?
Power(W) = energy transferred(J)/time(s)
What is efficiency?
The percentage of total input energy/power that’s converted to useful output energy.
What is the equation for efficiency (%)?
Efficiency = (useful energy or power / total energy or power)*100 (<- to turn decimal into percentage)
Thermal energy tends to leave buildings through..?
Conduction. Transferring energy to the outside surroundings -> insulation reduces this.
Describe the insulation practical.
- Pour hot water into a beaker and start the timer when the temperature hits 80°C.
- After 120s, measure temperature and record
- Repeat steps 1 & 2 with different types of insulation wrapped around the beaker, e.g wool
What is an energy source?
The sources from which we harness energy.
Name the non-renewable energy sources.
- Fossil fuels (coal, oil and natural gas) -> running out
- Nuclear fuel (uranium) -> not running out
Name the renewable energy sources.
- Wind power (turbines)
- Hydroelectric (water behind a dam falls through a turbine generating electricity)
- Biofuels (plant matter burned to produce heat)
- Geothermal (cold water evaporated by hot rocks; the steam turns a turbine powering a generator)
- Tidal (waves and tides rotate turbines, turning a generator)
How is energy supplied to electrons?
By a cell/battery or mains electricity - which then move through the wires to transfer energy.
How do circuits make lamps light up?
- Electrons have charge.
- Their charge travels from the cell/battery to the lamp where all their energy is converted into light.
- Charge returns to cell to gain more energy.
repeat
How does current/charge flow?
From + to -.
What is the measurement for charge?
Coulombs (groups of electrons)
What is p.d.?
The potential difference (voltage). It’s a measure of how much energy is transferred to/by each COULOMB of electrons/charge. It’s measured in volts.
How do you calculate p.d.?
p.d. (V) = energy transferred (J) / charge (C)
V = E/Q
How do you calculate energy transferred?
E = QV
Rearrangement of p.d. equation.
What is a voltmeter and how is it connected?
Voltmeters measure volts and are always connected in parallel to components.
What is current?
The rate of flow of charge, measured in Amps.
How do you calculate current?
current (A) = charge (C) / time (s)
I = Q/t
How do you calculate charge?
Q = It
The current equation rearranged.
What is an ammeter and how is it connected?
Ammeters measure amps and are always connected in series with a component.
What is resistance?
The measure of how much a component/object resists the flow of current. Measured in Ohms.
How do you calculate resistance?
Find a point on an IV graph on the line and rearrange Ohm’s law.
How does current vary with potential difference using a fixed resistor?
There is a straight line through the origin meaning V & I are directly proportional. There is a constant gradient and so constant resistance.
Due to this, it is ‘ohmic’.
(an ohmic conductor)
If another resistor gives a steeper gradient, it must have a lower resistance.
How does current vary with potential difference using a filament lamp?
The line curves, meaning the resistance isn’t consistent. A larger current results in an increased resistance.
Due to this, it’s non-ohmic.
Why is resistance inconsistent when using a filament lamp?
Delocalised electrons colide with the ionic lattice, which causes them to vibrate more and the temperature increases.
How does current vary with potential difference using a diode?
Diodes only let current flow in one direction. There’s low resistance in the forward direction and high resistance in the reverse direction.
Explain the practical to find the I/V characteristics of components.
- Create a circuit with a cell, variable resistor, voltmeter & fixed resistor and ammeter.
- Use voltmeter to read the p.d. across the resistor
- Use the ammeter to read the current through the resistor and record the values in a table
- Adjust the variable resistor and record new readings on the voltmeter and ammeter (must be done several times to get a range of readings)
- Switch direction of battery, switching the direction of the P.D. - the voltmeter and ammeter should have negative values (repeat step 3)
Repeat steps 2-5 with a circuit that has a [cell, variable resistor, voltmeter & filament lamp and ammeter] and a circuit that has a [cell, variable resistor, voltmeter & diode, millammeter and extra resistor].
The parts of the list written A&B mean A and B are in parallel.
What is Ohm’s law?
p.d. (V) = resistance (Ω) * current (A)
V = IR
How do you obtain negative values of p.d. and current?
Reverse the cell within a circuit.
What are 3 features of series circuits?
- Total p.d. is shared between all components
- Current is the same for all components
- Total resistance = sum of resistance
What is the rule of thumb for series circuits?
- If resistors are identical, total V must be shared equally.
- If not, the bigger resistance takes the bigger share of voltage.
What are 3 features of parallel circuits?
- p.d. for each branch = p.d. of cell/battery
- current is split between the branches
- adding more resistors in parallel reduces the total resistance (this is because current has more routes, so flows faster)
How does a thermistor react to a temperature increase within a circuit?
- Temp increases
- R of thermistor decreases
- Thermistor gets a smaller share of the total voltage
- The resistor gets a bigger share of the total voltage
- Voltmeter reading increases which could be used to turn off heating
How do LDRs react to light intensity decreases?
- Light intensisty decreases
- R of LDR increases
- LDR gets a bigger share of total voltage
- Voltmeter reading increases, which could be used to trigger a light to turn on
What can thermistors and LDRs be useful in?
Potential divider circuits to detect changes in the environment.
In the context of electricity…
How else can power be calculated?
power = current * p.d
OR
power = current2 * resistance
What is direct p.d. and what does it result in?
It’s a p.d. that only acts in one direction that results in direct current.
What is A.C.?
Mains electricity - Alternating current resulting from an alternating P.D.
What is the neutral wire?
The blue wire that goes through the left - it’s kept at 0V by the electrical company.
What is the live wire?
The brown wire which goes through the right. It changes between positive and negative potentials and carries the high voltage.
What is the earth wire?
The green and yellow wire, goes through the middle - it’s a safety feature.
It acts as an ‘escape route’ for the currents that would otherwise cause shock if the appliance is touched.
It’s not mandatory nor necessary for double insulated appliances.
What is a fuse and what is it connected to?
It’s a thin metal wire in a tube that’s designed to melt or ‘blow’ if there’s a fault that causes a high current. It’s always attached to a live wire.
How do power stations get energy to homes?
Power station -> step-up transformer -> national grid cables -> step-down transformer -> homes/businesses.
How do power stations reduce current that goes from the power station to the nat grid cables and increase current going from nat grid cables to homes?
A step up transformer to increase the voltage, decreasing current and reducing power lost due to heating in cables and a step down transformer to reduce the voltage down to a safer and usable voltage.
(If P in = P out, V&I are inversely proportional.)
What does density tell you?
How compact mass is for an object.
What is the equation for density?
ρ = m/v
density(kg/m3) = mass(kg)/volume(m3)
ρ is the greek letter ‘ro’
Describe the practical for finding the density of a regular object.
- Find the mass using a top-pan balance and record it
- Volume can be calculated by taking the measurements with a ruler (resolution 1mm) and doing the following calculation: area*length
- Then use ρ = m/v
Describe the practical for finding the density of an irregular object.
- Find the mass using a top-pan balance and record it
- Find and fill a displacement can with water to the spout.
- Carefully and slowly submerge object in water (using string) and wait for all water to be displaced out into a beaker placed at the spout
- Pour water within beaker into a measuring cylinder and take volume by getting on eye-level and using the bottom of the meniscus line
- Calculate density using ρ = m/v
What are the attributes of a solid?
- Particles are in a regular arrangement
- Particles vibrate at fixed positions
- They can’t be compressed
What are the attributes of a liquid?
- Particles arranged in an irregular arrangement
- Particles can move past each other
- They can’t be compressed.
What are attributes of a gas?
- Particles are far apart
- They can move past each other and collide
- Particles move quickly
- They can be compressed
What must there be in order for something to melt or evaporate?
Energy must be supplied to overcome the electrostatic forces of attraction between particles.
State the changes of state for: Solid -> Liquid -> Gas
Solid -> liquid: melt
Liquid -> gas: evaporate
State the changes of state for: Gas -> Liquid -> Solid
Gas -> liquid: condensing
Liquid -> solid: freezing
State the changes of state for: Solid -> Gas and Gas -> Solid
Solid -> Gas: sublimation
Gas -> Solid: deposition
What is internal energy?
The sum of kinetic energy and potential energy of all particles in a substance. Only one changes at any time.
Describe what happens on a graph depicting the heating curve for water.
When the temperature rises, the kinetic energy in particles rises. When temperature is static, the potential energy rises.
During changes of state, what’s the energy going in being used for?
It’s being used to overcome the electrostatic forces of attraction between particles.
What is the equation for thermal energy?
Same as SHC/thermal energy equation. △thermal energy(J) = mass(kg)*specific heat capacity (J/kg°C)*△temperature(°C)
What is SHC?
Specific Heat Capacity - the energy required to raise the temperature of 1kg of a substance by 1°C.
e.g. 4200J/kg°C for water.
What is the equation for potential energy?
E = mL
Potential energy (J) = mass (kg)*specific latent heat(J/kg)
What is SLH?
Specific Latent Heat - the energy required to change the state of 1kg of a substance.
e.g. SLH of fusion for water is 334000J/kg
What is gas pressure?
The result of gas particles colliding with the walls of its container, exerting outward force.
What are the effects of heating a gas?
It increases the gas particles’ kinetic energy, meaning they collide more frequently and with a greater force. This raises pressure.
How do you compress a gas?
Exert a force on it and raise pressure through turning up the temperature.
What is the relation between pressure and volume when gas is compressed at a constant temperature?
Pressure and volume are inversely proportional. When one doubles, the other halves.
The equation to show this is pV = constant
pressure (N/m²)*volume(m³)
Thanks to this; p1V1 = p2V2
What is the unit of pressure?
Pascals (Pa) which is the same as N/m²
What are the two types of force?
Contact and non-contact.
Give 3 examples of contact force.
Friction, air resistance and tension.
Give 3 examples of non-contact force.
Magnetism, electrostatic force and gravity.
What is a scalar? (give 3 examples)
A quantity with only magnitude. (distance, speed, and temperature)
What is a vector? (give 3 examples)
A quantity with a magnitude AND direction. (displacement, velocity and acceleration)
What is resultant force?
The sum of the 2 (or more) forces acting on an object. If 2 forces are at a right angle, use pythagoras’ theorem or trigonometry.
remember for trig: SOH CAH TOA!!
What is a balanced force?
A force that doesn’t change velocity and has no resultant force.
What is weight?
The force that gravity pulls an object down with.
What’s the equation of weight?
Weight (N) = mass(kg)*gravitational field strength(N/kg)
W = mg
What is the earth’s gravitational field strength?
9.8N/kg
When holding or lifting an object at a constant speed, how much force are you pushing upwards with?
The same as its weight.
What’s the equation for work done?
Work done(J) = force(N)*distance(m)
W = Fd
What is work done?
Energy transferred by a force.
What is Hooke’s law?
The force and extension of an object which deforms elastically are directionally proportional.
What is the equation representing Hooke’s Law (a.k.a. the spring constant equation)
Force(N) = spring constant(N/m)*extension(m)
F = ke
What is the practical demonstrating Hooke’s Law?
- Set up a clamp and stand with a spring hanging off the clamp and a mass hanger attached. Place a ruler parallel to the stand.
- Add masses onto the spring to change force in 1N increments.
- Measure the extension of the spring with the ruler after each mass is added.
- Plot results on a graph. Gradient = Spring Constant.
What errors can come with the Hooke’s Law experiment, and how can we solve them?
- There can be a systematic error with measuring. Avoid it by lining up 0cm with the bottom of the spring.
- There can be a random error by misreading the ruler due to perspective. Avoid this by getting eye level with the measurement when measuring.
What is a moment and how do you calculate one?
A turning force.
moment (Nm) = force (N) * distance from pivot (m)
What is the principle of moments?
When the sum of clockwise moments = sum of anticlockwise moments a system is in equilibrium.
How can gears be used in relativity to moments?
They can be used to increase moments by driving a large gear with a smaller one (they work on ratios: double the diameter, double the moment or ‘torque’)
What is the equation of pressure?
Pressure (N/m2 or Pa) = force (N) / area (m2)
Why do we feel pressure underwater?
This is due to the weight of the water above us pushing down on us.
What is the alternate equartion for pressure?
Pressure (N/m2) = height (m)*density(kg/m3)*g(N/kg)
P = Lρg
What is pressure in a gas due to?
The particles colliding with the walls of its container.
How do you increase the pressure in a gas?
- Decrease the volume and add more gas (creating more frequent collisions)
- Increase the temperature (more frequent collisions - faster speed and collide with more momentum - greater force)
To decrease would be the reverse.
When altitude rises, what happens?
The atmosphere gets less dense and there is less pressure.
How do you find the speed/velocity on a distance/displacement-time graph?
The gradient.
velocity (m/s) = distance or displacement (m) / time (s)
v = d/t
How do you find the acceleration on a speed/velocity-time graph?
The gradient. acceleration (m/s2) = change in velocity (m/s) / time (s)
a = △v/t
How do you find the displacement in a speed/velocity-time graph?
The area under the gradient.
What’s SUVAT?
S - displacement(m)
U - initial velocity (m/s)
V - final velocity (m/s)
A - acceleration (m/s2)
T - time (s)
Give the SUVAT equations.
- v = u + at
- s = (u+v/2)*t
- s = u*t+0.5*a*t2
- v2-u2 = 2*a*s
What’s Newton’s first law?
If no resistant force acts on an object, its motion will be constant.
What is inertia?
The tendency for an object’s motion to stay constant if there’s no resultant force.
What is terminal velocity?
An object experiences terminal velocity when the drag force = other force acting on it.
What is Newton’s second law?
Force (N) = mass (kg)*acceleration(m/s2)
Can newtons first and second law act on an object at the same time?
No.
What is the practical to prove f = ma
f is force, m is mass and a is acceleration
Accelerate trolley on tract with slotted mass on string over pully
- Use photogates to measure acceleration
- Change force by removing masses and placing them on the trolley.
- Plot force against acceleration. The gradient = total mass.
What is Newton’s third law?
For every action there’s an equal and opposite reaction. This is always true.
What is stopping distance?
Thinking distance + breaking distance.
What can thinking distance be affected by?
Speed (proportional), distractions, alcohol, drugs, fatigue.
What can breaking distance be affected by?
- Speed (proportional with a ratio of 1:12 because Ek = 0.5*m* v2)
- Condition of brakes, tyres and road
- Weather conditions
How do you calculate momentum?
momentum (kgm/s) = mass (kg)*velocity(m/s)
momentum = mv
In collisions, how is total momentum affected?
Conserved.
What is the equation for momentum in a rebound collision?
m1u1 = m1v1 + m2v2
What is the equation for momentum in a coupling collision?
m1u1 = mv
What is the equation for momentum in a recoil collision?
0 = m1v1 + m2v2
What is force?
The measure of the rate of change of momentum.
In the context of momentum…
What is the equation for force?
force = change in momentum / change in time
force = △momentum/△time
As time goes on, what happens to the momentum and force?
As time goes on and momentum is lost or gained, the force exerted is lost and vice versa.
Name some components of cars which increase collision time, and why it’s important.
- Seat belts
- Air bags
- Crumple zones
They increase collision time, so momentum is lost over a longer time, reducing force and therefore harm possibly caused.
Do waves transfer energy, matter or both?
Waves transfer energy but not matter.
Which way do longitudinal waves oscillate?
Parallel to the direction of energy transfer.
Which way do transverse waves oscillate?
Perpendicular to the direction of energy transfer.
What does a longitudinal wave consist of?
Compressions and rarefactions.
Give two examples of longitudinal waves.
Sound waves and seismic P waves
Give two examples of transverse waves.
Water waves and light waves.
What is a wavelength?
The length of one complete wave.
λ
What is a time period?
The time taken for one wave to pass.
Define frequency.
The number of waves that pass every second.
What is the wave equation?
wavespeed (m/s) = frequency (Hz) * wavelength (m)
v = fλ
Explain the ripple tank practical.
- You will need a ripple tank with white paper beneath it, a lamp above it, water within the tank and a vibrating bar in the water connected to a power pack.
- Place a ruler on the paper, and record the ripple tank’s shadows as the vibrating bar is on.
- Use a frame of the video to measure the distance of 10 wavelengths. Then divide it by 10, giving the wavelength of these waves.
- Then mark a point on the paper, place a timer next to the paper and record again for 15 seconds.
- Trim the video to 10 seconds and count the number of waves passing the point you marked in that time in slow motion. Then divide by 10, finding the frequency.
- Then use the wave equation to find the wave speed.
v = f * λ
Explain the waves in a solid practical.
- Set up a string attached to a vibration generator and a hanging mass. Hang the mass on with a pulley on a clamp (to keep the string taut) and keep the string level with a wooden bridge. Control the frequency of vibration using a signal generator connected to the vibration generator.
- A certain frequency, the string becomes a standing wave due to resonance (looks like ♾️)
- Measure the wavelength of the standing wave using a ruler (the distance between the wood bridge and the vibration generator)
- Use the wavelength and frequency to calculate the speed of the wave (v = λ*f)
Wavespeed depends on the taughtness of the string and the mass/cm.
How can you tell the pitch and volume of a sound by looking at the sound wave?
Higher frequency = higher pitch
Greater amplitude = louder
What is the human hearing range & what range of frequency is ultrasound?
The human hearing range is 20Hz - 20kHz. Anything above 20kHz is ultrasound.
What can happen to a sound wave when it meets a boudnary between two mediums?
Some sound is transmitted, some is reflected.
How does sonar work?
When sound meets a boundary between two mediums the sound is either transmitted or reflected. Resulting echoes can be timed to build up an image of what’s out of view.
Sonar is used for ultrasounds and fish underneath boats.
What type of wave can travel through liquid?
Longitudinal waves.
e.g. seismic P-waves.
Give the evidence that the earth has a molten core.
- Seismic P-waves are longitudinal and pass through the centre of the earth.
- S-waves are transverse and don’t pass through the centre of the earth.
- As S and P waves are sent through one end of the earth only P-waves are detected on the other side, suggesting there is a molten (liquid) core within the earth.
Define specular reflection.
Light reflecting off a smooth surface. The angle of reflection is equal to the angle of incidence in relation to the normal.
Define diffuse reflection.
Light reflecting off a rough surface, scattering it.
State the electromagnetic spectrum in order of longer to shorter wavelengths.
- Radio waves
- Micro waves
- Infra-red
- Visible light
- Ultra violet
- X-rays
- Gamma rays
All EM waves are emitted and absorbed by what, and name the exception.
Emitted and absorbed by electrons, except from gamma which is emitted by nuclei.
If the energy of a wave is high enough, what happens?
It can cause an electron to leave its atom, leaving an ion behind. This is ionising radiation.
UV, X-rays and gamma rays do this.
Give 3 examples of radio waves.
- Phones
- TV
- WiFi
Give an example of microwaves.
- Cooking (absorbed by water)
Give an example of infra-red
Cooking (absorbed by surface).
Give a use of visible light.
Vision.
Give a use and 2 dangers of UV rays.
Tanning. It can cause skin cancer and ionising radiation.
Give a use for x-rays and gamma rays, and state why they’re dangerous.
- X-rays can be used for medical scans
- Gamma rays can be used for sterilising, medical treatments
Both are dangerous as they have ionising radiation.
Explain the infrared practical(s).
pt 1:
A leslie’s cube has a shiny metallic surface, a white surface, a shiny black surface and a matt black surface.
1. Fill leslie’s cube with hot water
2. Point an infrared detector at each of the four surfaces and record the amount of infrared emitted (must keep same distance between leslie’s cube and detector)
The matt black emits the most infrared radiation. Then shiny black, white and shiny metallic.
pt 2:
1. Infrared heater with two metal plates on either side. One plate is shiny metallic and the other is matt black
2. Vaseline has been used to attach a drawing pin to the outer side of each plate
3. Turn on the heater and a timer
4. Record the time it takes for the vaseline to melt and drawing pins to fall off
The drawing pin falls off the matt black plate first. Matt black surfaces absorb more infrared radiation than shiny metallic surfaces.
Matt black surfaces are the best emitters and absorbers of infrared radiation.
Explain refraction.
When waves enter a new medium, their speed and angle changes.
If the speed decreases, so does wavelength, while frequency is always constant.
What happens when a wave slows down?
It bends towards the normal. This means the angle of refraction will be smaller than the angle of incidence.
And vice versa. If the wave speeds up, it bends away from the normal.
Why do you get a rainbow when you shine light through a prism?
Because the light disperses; the difference wavelengths are refracted different amounts (blue most, red least).
How do lenses work and what are the two types?
They use refraction to make light rays converge or diverge. There is convex and concave.
How do convex lenses focus an image?
They bend light rays towards the principal focus, which is in the middle of the principle focus.
What does a convex lens look like drawn and what is the focal length?
The focal length is the length of the lens, and a convex lens looks like this:
|
v
How do you see where an image is formed through a convex lens?
- Draw two rays from the top of the object:
1. Straight through the centre
2. Parallel in, then through the principle focus. - If the two rays don’t meet, extrapolate through dotted lines backwards and see where they meet that way.
- Then draw the image from the principle axis to the point where the rays meet.
What is the difference between real and virtual images?
Real images can be projected, virtual images can’t (as the rays meet on the wrong side of the lens.
How do you see where an image is formed through a concave lens?
- Draw two rays from the top of the object:
1. Straight through the centre
2. Parallel in, then away from the principle focus. - Then extrapolate the 2nd ray backwards.
- Draw the image from the principle axis to the point where the rays meet.
State the 3 characteristics of an image.
- real/virtual
- upright/inverted
- magnified/diminished
How do you calculate magnification?
magnification = image height / object height
How do we perceive different colours?
Different wavelengths of light are absorbed by the retina. An object will appear a certain colour as it reflects those wavelengths and absorbs others.
Define a blackbody.
A theoretical object that perfectly absorbs and emits all wavelengths of radiation (it doesn’t reflect radiation). It can be applied to stars and planets as an approximation.
How does the temperature of an object increase?
If the rate of absorption is greater than the rate of emission, the temperature increases. However this also increases the rate of emission.
State the planets starting from the closest to the sun.
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
mnemonic: my very easy method just set up nine planets.
What galaxy are we in?
The milky way, containing many solar systems.
Explain the beginnings of a star.
- Nebula: dust particles are attracted by gravity.
- Proto star
- Main sequence star: pressure from fusion balanced with gravitational pull.
Explain the death of a star with a similar size to our sun.
- Red giant: outward pressure increases causes it into expand.
- White dwarf: fuel has run out
- Black dwarf: cooled
Explain the death of a star bigger than our sun.
- Super red giant: outward pressure increases until it expands
- Supernova: produces heavy elements and a new nebula
- Neutron star: if very dense
- Black hole: so dense, gravity is so strong that light can’t even escape.
What are the two types of satellites?
And one subtype.
- Natural satellites = moon
- Artificial satellites = space stations
These two orbit the earth. - Geostationary satellites orbit above the same point on the equator.
e.g. gps, tv, communications
Explain the orbit of satellites.
- Orbits are circular
- Speed is constant
- Direction changing
- Meaning velocity is changing
- Accelerating but not getting faster
What is the centripetal force?
Always acts towards the centre of the orbit.
What angle are the velocity and centripetal force of a satellite always at in relation to each other?
A right-angle (90°)
What happens if a satellite has an elliptical orbit, and what are elliptical satellites used for?
- As it gets faster it gets closer to the earth and vice versa.
- Used for reconnaissance and weather.
Explain red-shift.
The wavelength of light from distant galaxies is stretched because the galaxies are moving away from us.
Further galaxies are MORE red-shifted, meaning they’re receding at a greater rate.
Explain two pieces of evidende for the big bang theory.
- Red-shift suggests at one point all our galaxies originated from the same position.
- CMBR a.k.a. cosmic microwave background radiation is detected from every direction of space, which could be from the matter still cooling down from the Big Bang.
