Physics Paper 2- Major Focus Of Exam Flashcards
What is an oscillation?
A wave movement up or down.
What direction are oscillations to the direction of energy transfer in a transverse wave?
Perpendicular
What direction are oscillations to the direction of energy transfer in longitudinal wave?
Parallel
In a longitudinal wave, what are compressions?
Where particles are close together
In a longitudinal wave, what are rarefactions?
Where particles are spread apart.
What type of wave requires a medium?
A longitudinal wave
Do all transverse waves require a medium?
No
What is the wavelength of a wave?
Distance from a point on one wave to the equivalent point on the adjacent wave
What can the wavelength on a longitudinal wave be from?
One compression to another, or one rarefaction to another
What is the frequency of a wave?
Number of waves passing a point each second
What is the unit for frequency ?
Hertz(Hz)
What’s the equation for frequency?
1/time period
What’s the equation?
Wave speed=frequency x wavelength
What is the wave speed of a wave?
Speed at which a wave moves through a medium
In a practical of the speed of sound in air, what equipment do person a and b have?
A has cymbals, B has a timer
Describe the practical of investigating speed of sound in air
Person B starts timer when they see person a clash the cymbals.
Person B stops the timer when they hear it.
Measure time taken
Divide the distance they are spectated by the time.
What’s the problems of the practical when investigating speed of sound in air?
Time depends on reaction time.
Time is very short, so difficult to stop quickly.
How can the problems in the practical of investigating speed of sound in air be solved?
Has more people observing with timers.
Increase distance between each person
What are the 3 ways waves can be transferred?
Transmitted
Absorbed
Reflected
What does the action of the wave(absorbed or reflected) depend on?
Wavelength and type of material
What is the angle of incidence equal to?
Angle of reflection
What equipment is needed when completing the reflection/refraction practical?
Ray box,
Lens and slit.
After you complete the practical of reflection and refraction involving a glass block, what do you
Do?
Repeat and use a different material
What type of waves are sound waves?
Longitudinal
What is the range in Hz of human hearing?
20-20,000hz
Why doesn’t the frequency change when a wave changes medium?
A wave would have to be created or destroyed
What quality is frequency responsible for?
Pitch
What quality is amplitude responsible for?
Loudness
Where do sound waves only move?
Through a medium
How do sound waves move?
By vibrating particles
Why can’t sound waves pass through a vacuum?
No particles
What is a reflected sound wave also known as?
An echoe
What is the frequency of ultrasound waves?
> 20,000Hz
What are ultrasounds partially reflected at a boundary between?
2 different densities
What images can ultrasound waves produce?
Internal organs and images of the foetus
What can patterns of seismic waves give info about?
The Earth’s interior
Are P waves longitudinal or transverse?
Longitudinal
Give 2 other differences between P and S waves( besides type of wave)
P waves can pass through both solids and liquids, whereas S waves can only travel through solids.
P waves travel faster than S waves in solids.
It is true that S waves are transverse?
Yes
What does the S wave shadow zone tell us?
No waves are detected by the earths core, therefore it must be liquid as S waves can’t pass through liquids.
What does the P wave shadow zone provide evidence for?
That the earth has a liquid core.
How does the P wave shadow zone provide evidence for the earths liquid core?
Travel faster in solids and slow down as they enter liquids, seen as they are refracted after passing through the Earths core.
When a wire is carrying a current, what does it experience?
A force in a magnetic field
How can we determine the direction of the force?
By using Flemings left hand rule
What is a split ring commutator ?
A metal ring that switches the direction of current when the loop passes 90 degrees
What do split ring commutators have that allows current onto the ring?
Brushes
What makes a motor turn in the clockwise direction?
The force
By switching the direction of current, what does the split ring commutator allow the motor to keep?
Rotating in the same direction
What is the motor effect?
When 2 magnets are placed close to each other and the magnetic fields affect each other and produce a force
What’s the equation for force?
Magnetic flux density x current x length
What’s does the equation for force only apply to?
A wire that is at right angles to the magnetic field
Unit for magnetic flux density
Tesla
In Flemings left hand rule, what does the first finger represent?
Magnetic field
In Flemings left hand rule, what does the second finger represent?
Direction of current
When will a conductor not experience a force?
When it’s parallel to the magnetic field
What’s does the strength of the magnetic field depend on the size of?
The current
Besides with a larger current, when is the magnetic field strongest?
Closer to the wire
If we change the direction of the current, what else do we change
The direction of the magnetic field
What rule do we use to work out the direction of the magnetic field?
Right hand grip rule
In the right hand grip rule, what does the thumb represent?
Conventional current
How else can we increase the strength of a magnetic field?
Coil the wire into a solenoid
When we turn on the current in a solenoid what do we get?
A strong and uniform magnetic field
What’s the magnetic field around a solenoid have a similar shape to?
The magnetic field around a bar magnet
What are 3 ways we can increase the strength of a magnetic field around a solenoid?
Increase current
Increase number of turns of coil
Place iron inside it - core
What’s a solenoid containing an iron core called?
An electromagnet
Why are electromagnets useful?
We can change the strength of the magnetic field by changing size of current
Can be turned on and off
What are radio waves used for?
Transmitting radio and trrrestrial TV signals
Why are radio waves used in transmitting radio signals?
They can travel long distances before being absorbed
Can spread out between hills
Reflect off a layer of ions in the atmosphere
What are microwaves used for?
Heating food
Communicate with satellites in space
Why are microwaves used in heat foods?
Foods contain water molecules
Water molecules absorb energy of microwaves
Why are microwaves used in communicating with satellites
Waves can pass through atmosphere without being reflected or refracted
What’s infrared emitted by?
Electrical heaters
What is infrared used in
Cooking food in ovens
Cameras
Why is infrared used to cook food in ovens?
Energy is easily absorbed by surface of objects
What’s a use of visible light?
Communication using fibre optics
What are optical fibres
Thin strands of glass
Why are optic fibres useful!
Can transmit pulses of light down it to carry information
What are optical fibres used to carry?
Telephone and cable TV signals
Why can visible light carry lots of information?
Short wavelength
What’s 2 uses of ultraviolet?
Energy efficient lightbulbs
Sun tanning
Why does UV carry more energy than visible light?
Shorter wavelength
How is Uv used in lightbulbs?
Energy is UV is absorbed by the internal surface of the bulbs and is converted to visible light
What does UV increase the risk of?
Skin cancer
What’s are both x rays and gamma rays used for?
Medical imaging
What are x rays more specifically used for?
Visualising broken bones
What can gamma rays detect?
Cancers
Why are x rays and gamma rays used in medical imaging!
They are highly penetrative
What type of satellites are moons?
Natural
What is a galaxy?
A massive group of stars
Describe how stars like the sun are formed
Clouds of dust and gas- nebula
Gravity causes this to collapse- protostar
Temperature rises due to particles moving faster
Hydrogen nuclei fuse to form helium= nuclear fusion
=star
What do scientists say the sun is in equilibrium?
Inward force of gravity is balanced by outward force of fusion
What does nuclear fusion release lots of?
Energy
What happens to stars the same size as the sun?
Main sequence
Hydrogen runs out- outward force of fusion is less than inward force of gravity- stars collapses inwards
Helium nuclei fuse to create heavier elements
Expands and Forms a red giant
Fusion stops, star shrinks and forms a white dwarf
This cools down
Stops releasing energy and forms a black dwarf
Why does the white dwarf cool down to form a black dwarf?
No longer fuses
Describe the lifecycle of stars bigger than the sun
Main sequence Red super giants Helium nuclei fuse to produce heavier elements Stops fusion- explodes as a supernova Make elements heavier than iron Form a neutron star or a black hole
Why are elements heavier than iron only produced in a supernova?
The temperature is very high
What 2 objects can form after a supernova?
Neutron star or a black hole
What holds the earth in its orbit?
Force of gravity acting between the sun and earth
How often do geostationary satellites orbit?
Once every 24 hours
In the case of circular orbits, what does gravity lead to?
A change in velocity
Why does gravity lead to a change in velocity but not speed?
Direction is constantly changing, so velocity is as well as it’s a vector quantity
If the speed of a satellite increases, what happens to the radius of its orbit?
It decreases
Why if the speed is higher, the radius of its radius is lower?
At snigger speed, a greater force of gravity is needed to prevent it flying off into space
What does red shift tell us?
Galaxies are living away from each other
What must the light waves be when the galaxies are moving away?
Stretched
Does galaxies further away have a bigger or smaller red shift?
Bigger
Why are far galaxies moving faster than galaxies that are closer?
They have a bigger red shift
What provides evidence that the universe is expanding?
Fact that distant galaxies are moving faster than nearby galaxies
Where do scientists believe the universe began from?
A very small region that’s as hot and dense
What could explain why the expansion of the universe is speeding up?
Universe contains matter and dark energy we can’t detect
What is Newton’s third law of motion?
It states when 2 objects interact with each other, they exert an equal and opposite forces on each other
What force makes a car move?
The driving force
What is Newton’s first law of motion?
It states if forces acting on an object are balanced, the resultant force is zero or if the object is at rest stays stationary
What type of diagram shows the forces acting on an object?
Free body
What’s Newton’s second law of motion?
F=MA
Describe how to measure speed of sound in air
Set up oscilloscope so rested waves at each microphone are shown as separate waves
Start with both microphones next to speaker, then slowly move one away until the 2 waves are aligned on display
Measure distance between microphones to find wavelength
Find speed using the wave equation
Describe how to measure speed of water ripples using a lamp
Dim light and turn on lamp- can see wave pattern made by shadows of crests
Measure distance between shadow lines that are 10 wavelengths apart and divide by 10 to find average
Can you wave equation to find speed
Why is measuring speed of water ripples using a lamp suitable?
Can take a photo of shadow and find distance using a ruler
Don’t have to disturb waves
Describe the practical involving ray box
Place transparent block on paper and trace around it
Use ray box to shine light at middle of block
Trace incident ray and mark where ray emerges on the other side
Remove block and with a straight line join up the incident and emerging ray to show refracted ray
Draw normal
Use protractor to find angle of incidence and angle between normal and refracted ray
Repeat experiment using blocks of different materials
What’s a strength and a weakness of the balloon model
As balloon expands, dots get further apart- represent galaxies moving apart
W: dots are only on surface, galaxies are throughout universe
Balloon can pop
How can you get accurate magnification values for high distances
Use tall
Object
How can you show that a magnetic field has been produced around the wire
Move a compass around wire, changing direction of compass shows magnetic field has been produced
How does the ignition circuit work?
Closing switch causes current to pass through electromagnet Iron core becomes magnetised Code attracts iron arm Iron arm pushes the contacts together Starter motor circuit is complete Current flows through it
Possible source of inaccuracy for ray box practical
Width of light ray makes it difficult to judge where centre of ray is
Why is light refracted as it crosses from air into glass
Velocity of light decreases
Why is iron a suitable material for the core of a transformer?
It is easily magnetised
How can you tell something is a step down transformer based of coils
Potential difference across secondary coil is less than the primary coil
Why do scientists publish results despite them not being able to explain them
Allow peer review
Promote further experiments
Explain how a train can accelerate without changing speed
Train changes direction so velocity changes, and acceleration is the rate of change of velocity
What’s braking distance?
Distance travelled under the braking force
Explain why stopping distance of car increases if driver is very tired
Reaction time increases
Increased thinking distance
Why does atmospheric pressure decrease with increasing altitude
Fewer air molecules
Number of collisions with a surface decreases
Air molecules colliding with a surface create oressure , so
Less oressure
Why are windows designed the way they are?
Force from air pressure acting from side to outside is bigger than force acting upwards
Keeps window in position
Explain how a loudspeaker converts current in an electrical circuit to a sound wave
Current in circuit is varying
Current passes through coil
Coil
Experiences a force
Varying current causes coil to vibrate, causing a fine to vibrate
This causes air molecules to move and produces pressure variations in air needed for a sound wave
Explain how the structure of the ear allows us to hear noises
Sound waves ear drum to vibrate
Nerves are converted into information
Only works at certain frequencies
Why doe refraction occur when a wave moves between 2 different mediums
Velocity changes when there’s a change in direction
Explain the change in pressure as you move away from earth
Decrease in pressure
Fewer particles colliding with surface due to fewer particles higher up
Total number of particles contribute to total atmosphere pressure
Explain how red shift has supported the theory that universe is expanding and Big Bang was origin of universe
Observe distant galaxies moving further away quicker
Universe is expanding from a single point
If an object isn’t moving, what’s its momentum
0
Typical speed off a person walking
1.5m/s
Running
3m/s
Cycling
6m/s
Car
25m/s
Train
55m/s
Plane
250m/s
What do safety devices do to make us safer
Slow down rate of change in momentum and reduce forces acting on us
Explain why study of seismic waves provides evidence of structure of earths core
S waves didnt travel through core and can’t travel through liquid
Suggest what student may have done during investigation to cause each angle of reflection to have a range of values
Misjudged the centre of ray
Why does the velocity of a satellites change as it orbits earth
Force of gravity causes it to accelerate
This causes a change in direction, causing velocity
To change
Explain why scientists replace an old scientific model with a new model
New evidence
Evidence can’t be explained using existing model
New model explains new evidence
Eg nuclear mode of atom replacing plum pudding
Explain why refraction happens at a boundary between the deep water and shallower water
Velocity is slower in shallower water
So edge of wave entering shallow water slows down
But part of wave in deeper water continues at high speed
Explain why wave fronts do not retract at the boundary where they are all parallel
Every point on wave hits shallow water at same time so slow down at same time
When there’s current in a coil, the current rotates continuously, explain why
Sides of cool experience a drive
Force cause moments that act in same direction
2 halves of commutator swap from one brush to other
Commutator reverses current
Explain factors that affect distance needed to stop a vehicle in emergency
Reaction time- increases thinning distance from drinking alcohol
Speed- increases work down to stop vehicle- affected by condition of roads
Condition of brakes- less friction
Danger caused by vehicle having a large deceleration when it’s braking
Brakes lock
Loss of control
Explain how red shift supports how universe began from small hot dense region
Furthest galaxies are moving the fastest, suggesting universe is expandinf
What’s inertia
Tendency of an object to continue in its state of rest or motion
Explain why an egg is less likely to break when dropped onto soft foam rather than onto a concrete floor
Foam increases time taken to stop
Decreases rate if change in momentum
Reduces force
Explain the changing motion of a skydiver in terms of forces acting on him
Initially air resistance is less than weight so he accelerated
Accelerations causes air resistance to increase
Resultant force decreases to 0
Skydiver falls at terminal velocity
Explain why jumping from a higher distance allowed the skydiver to reach a higher passed than from a lower distance
Higher altitude=less dense air
So air resistance less
Skydiver can accelerate longer before reaching terminal velocity
Explain who a microphone works
Sound waves cause diaphragm to vibrate
Causes coil to vibrate
Coil moves through magnetic field
Potential difference is induced
Describe life cycle of starts bigger than sun
Cloud of gas pulled together by gravity
Cussing an increase in temp for fusion to start
A protostar forms
Hydrogen nuclei fuse to form helium nuclei and star becomes main sequence
Hydrogen runs out and helium fuse to make heavier elements up to iron
Start expands to become a red supergiant
It collapses and explodes in a supernova
This leaves behind a neutron star or black hole
Which property of a stat does range of wavelengths depend on
Temperature
Explain why using a wider ray would give elsss accurate results than using a narrower ray
Harder to judge centre of ray
Causing a larger uncertainty
What property of a light wave changes when it’s refracted
Velocity
Explain how protective pads help to reduce injury when players collide
Increase time taken to stop
Rate of change of momentum decreases
Reduced forcr
Why do cars have maximum speed
Maximum forward force provided by motor
As speed of car increases, air resistance increases
Until air resistance is equal to forward force
Car no longer can accelerste
Why is an alternating current induced in a coil
Coil cuts magnetic field lines
Pd is induced
There’s a complete circuit so current is induced
Every half turn the pd reversed direction
So current changes direction
Why does applying brakes cause the temperature of the brakes to increase
Work done by friction between brake and wheeels
Decrease on Ke and increase in thermal eneegy
Factors affecting thinking distance
Tiredness
Alcohol drugs
Factors affecting risking distance
Road surface
Condition of brakes
Tyres
How can you test if a spring behaves elasticslly
Remove force
Returns to original shake and kength
