paper 2

Question 1

formula with momentum, mass and velocity

Answer 1

momentum = mass x velocity

Question 2

formula with force, change in momentum and time taken

Answer 2

force = change in momentum / time taken

Question 3

unit for momentum

Answer 3

kg m/s

Question 4

principle of conservation of momentum

Answer 4

the total momentum before an interaction is equal to the total momentum after an interaction if no external forces are acting on the objects

the interaction can either be a collision where two objects collide with each other or an explosion where a stationary object explodes into two or more parts

Question 5

how to calculate mass, velocity or momentum of objects

Answer 5

calculate original momentum of each object then add together to get total momentum before
as total momentum before = total momentum afterwards calculate momentum of objects after
add momentum of objects after together and this number must =momentum before

Question 6

how to explain safety features using momentum

Answer 6

to reduce the force experienced by passengers extend the contract time as force = change in m / time so as change in momentum is constant by changing the time you can change the force.

cars have front and back crumple zone to absorb energy and extend the time taken for the impact which then also increases the time taken when the force acts which increases the time taken for the change in momentum to act reducing the force and risk of injury
airbags also deploy and are compressible so when you hit them your head compresses them so you are in contact with them for longer so the time taken is longer which decreases the force and deceleration over a longer time
seatbelts prevent you hitting the steering wheel and increases the time for you to stop so therefore decreases the force

Question 7

newtons third law

Answer 7

for every force that acts there is an EQUAL sized reaction force of the SAME type, SAME size but OPPOSITE direction
each force acts on DIFFERENT objects
for example, i am attracted to the earth by weight and the earth is attracted to me by weight

Question 8

formula with moment, force and perpendicular distance from the pivot

Answer 8

moment = force x perpendicular distance
so by opening a door far away from its hinge it is much easier as the distance is larger

Question 9

where does the weight of an object act through

Answer 9

its centre of gravity

Question 10

principle of moments

Answer 10

total moments clockwise = total moments anticlockwise in equilibrium

Question 11

unit for moment

Answer 11

Nm newton metre

Question 12

how to calculate force or distance from pivot using principle of moments

Answer 12

calculate the total moments clockwise and also total moments anticlockwise
if in equilibrium these will equal each other

Question 13

what are common materials that are electrical conductors or insulators

Answer 13

conductors:
Silver Copper Aluminium Steel

insulators:
Rubber Plastic Glass Wood

Question 14

practical: investigate how insulating materials can be charged by friction

Answer 14

Take a polythene rod, hold it at its centre and rub both ends with a cloth
Suspend the rod, without touching the ends, from a stand using a cradle and nylon string
Take an acrylic rod and rub it with another cloth
Without touching the ends of the acrylic rod bring each end of the acrylic rod up to, but without touching, each end of the polythene rod (if the ends do touch, the rods will discharge and the forces will no longer be present)
Record any observations of the polythene rod’s motion
Repeat, changing out the acrylic rod for rods of different materials

When two insulating materials are rubbed together, electrons will transfer from one insulator onto the other insulator
A polythene rod is given a negative charge by rubbing it with the cloth
This is because electrons are transferred to the polythene from the cloth
Electrons are negatively charged, hence the polythene rod becomes negatively charged
Conversely, an acetate rod is given a positive when rubbed with a cloth
This is because electrons are transferred away from the acetate to the cloth
Electrons are negatively charged, so when the acetate loses negative charge, it becomes positively charged

If the material is repelled by (rotates away from) the polythene rod, then the materials have the same charge
If the material is attracted to (moves towards) the polythene rod, then they have opposite charges

Question 15

explain how positive and negative electrostatic charges are produced

Answer 15

a positive charge is produced by loss of electrons
a negative charge is produced by gain of electrons

Question 16

how is there attraction and repulsion

Answer 16

like charges repel and unlike charges attract

Question 17

dangers of electrostatic charges

Answer 17

when a large amount of charge builds up, it produces a large potential difference across a gap
If the potential difference is large enough, current can travel through the air between objects – this is a spark
There are dangers of sparking in everyday situations such as fuelling vehicles such as cars and planes and the spark can cause a fire as the fuel is very flammable. (an earth wire stops this)

Question 18

how could a spark be produced by fuelling a vehicle

Answer 18

A build-up of static charge is a potential danger when refuelling aeroplanes
Fuel runs through pipes at a fast rate
This fuel is very flammable
The friction between the fuel (a liquid insulator) and the pipe causes the fuel to gain charge
If this charge were to cause a spark, the fuel could ignite and cause an explosion

This is prevented by the fuel tank being connected to the Earth with a copper wire called the bonding line during the refuelling
The conductor earths the plane by carrying the charge through to the Earth which removes the risk of any sparks
It is easier for charge to flow down the bonding line than to spark, so sparks are very unlikely to occur

Question 19

uses of static electricity

Answer 19

photocopiers + inkjet printer + insecticides + spray painting

Question 20

what is the frequency range of human hearing

Answer 20

20Hz - 20,000Hz

Question 21

practical: investigate the speed of sound in air

Answer 21

have 2 people stand 300 meters (measured with a trundle wheel) away from each other
one has a pair of cymbals and the other has a stopwatch
the person with the cymbals hits them together and then the stopwatch person starts the timer when they see the cymbals hit and stops it when they hear the sound.
record the time
repeat this 3 times and work out average time
s=d/t
increase distance and repeat

Question 22

how can a oscilloscope and microphone be used to display a sound wave

Answer 22

Microphone Connection: A microphone is connected to an oscilloscope. The microphone captures sound waves and converts them into electrical signals
Signal Conversion: The oscilloscope takes these electrical signals and converts them into a visual representation, displaying them as transverse waves on its screen

Question 23

practical: investigate the frequency of a sound wave using an oscilloscope

Answer 23

Connect the microphone to the oscilloscope

Test the microphone displays a signal by humming

Adjust the time base of the oscilloscope until the signal fits on the screen - ensure that multiple complete waves can be seen

Strike the tuning fork on the edge of a hard surface to generate sound waves of a pure frequency

Hold the tuning fork near to the microphone and observe the sound wave on the oscilloscope screen

Freeze the image on the oscilloscope screen, or take a picture of it

Measure the number of squares for one complete cycle

multiply the number of squares by the time base to find the time period

frequency = 1/T

Question 24

how does the pitch of a sound relate to the frequency of vibration

Answer 24

the higher the pitch of a sound, the higher frequency the wave has

Question 25

energy transfers involved in generating electricity using wind:

Answer 25

kinetic of wind -> mechanically -> kinetic of turbine -> mechanically -> kinetic of generator -> electrically to grid

Question 26

energy transfers involved in generating electricity using waves:

Answer 26

kinetic + gravitiational of water depleted -> mechanically -> kinetic store of generator -> electrically to grid

Question 27

energy transfers involved in generating electricity using geothermal:

Answer 27

chemical of earth is depleted -> thermal store of water -> kinetic store of water -> mechanically -> kinetic store of turbine -> mechanically -> kinetic store of generator -> electrically

Question 28

energy transfers involved in generating electricity using solar cells:

Answer 28

nuclear store of sun -> radiated light -> solar cell absorbs radiation -> electrically

Question 29

energy transfers involved in generating electricity using tidal:

Answer 29

gravitational water -> mechanically -> kinetic store of turbine -> mechanically -> kinetic store generator -> electrically

Question 30

energy transfers involved in generating electricity using fossil fuels:

Answer 30

chemical store of fuel -> thermal store of water -> kinetic store of steam -> mechanically -> kinetic store of turbine -> mechanically kinetic store of generator -> electrically

Question 31

energy transfers involved in generating electricity using nuclear:

Answer 31

nuclear store of uranium -> thermal store of water -> kinetic store of steam -> mechanically -> kinetic store of turbine -> mechanically kinetic store of generator -> electrically

Question 32

advantages and disadvantages of generating electricity by wind

Answer 32

Advantages – renewable, pretty cheap, no atmospheric pollution Disadvantages – non reliable, not very pretty, uses a large area, location dependent

Question 33

advantages and disadvantages of generating electricity by nuclear

Answer 33

Advantages – very efficient, a little bit of uranium creates a lot of energy, not location dependent, reliable, high energy density, carbon neutral Disadvantages – creates nuclear waste which is dangerous and can't be disposed of easily, can be very bad if it explodes

Question 34

advantages and disadvantages of generating electricity by fossil fuels

Answer 34

advantages - reliable and non location dependant disadvantages - non renewable and creates atmospheric pollution which contributes to global warming

Question 35

advantages and disadvantages of generating electricity by geothermal

Answer 35

Advantages – renewable, reliable, doesn't contribute to atmospheric pollution. Disadvantages – location dependent

Question 36

advantages and disadvantages of generating electricity by hydroelectricity

Answer 36

Advantages – very reliable, renewable Disadvantages – very expensive and time consuming to build, disrupts ecosystem, location dependent

Question 37

advantages and disadvantages of generating electricity by tidal/wave

Answer 37

Advantages – reliable, renewable Disadvantages – very expensive and time consuming to build, disrupts ecosystem, location dependent

Question 38

advantages and disadvantages of generating electricity by solar heating

Answer 38

Advantages – its renewable, it works all day and it reduces our carbon footprint Disadvantages – Expensive equipment cost, requires a large area to work, time dependent

Question 39

advantages and disadvantages of generating electricity by solar cells

Answer 39

Advantages – low maintenance, easy to install, reduces carbon footprint, no atmospheric pollution Disadvantages - Expensive equipment cost, Weather/daytime dependency, not very pretty, takes up large area

Question 40

what does J/kg'c measure

Answer 40

specific heat capacity

Question 41

arrangement and motion of particles in solids

Answer 41

regular fixed arrangement vibrate around a fixed position they also have A definite shape (they are rigid) A definite volume

Question 42

arrangement and motion of particles in liquids

Answer 42

randomly arranged move around each other liquids have no definite shape a definite volume

Question 43

arrangement and motion of particles in gases

Answer 43

randomly arranged move quickly in all directions gases have no definite shape or volume

Question 44

changes that occur when a solid melts into a liquid

Answer 44

Thermal energy transfer takes place and supplies the particles in the solid with energy in their kinetic store This breaks the rigid bonds between the particles meaning they can now flow over each other

Question 45

changes that occur when a liquid evaporates or boils into a gas

Answer 45

Thermal energy transfer takes place and supplies the particles on the surface of the liquid with energy in their kinetic store This removes the bonds between the particles meaning they can move about randomly and spread far apart

Question 46

why does a heating system change the energy stored in it

Answer 46

Heating a system will change the energy stored in a system by increasing the kinetic energy of its particles The temperature of the material, therefore, is related to the average kinetic energy of the molecules This increase in kinetic energy (and therefore energy stored in the system) can: Cause the temperature of the system to increase Or, produce a change of state (solid to liquid or liquid to gas) The higher the temperature, the higher the average kinetic energy of the molecules and vice versa This means they move around faster

Question 47

practical: obtain a temperature–time graph to show the constant temperature during a change of state

Answer 47

Place the ice cubes in the beaker (it should be about half full) Place the thermometer in the beaker Place the beaker on the tripod and gauze and slowly start to heat it using the bunsen burner As the beaker is heated, take regular temperature measurements (e.g. at one minute intervals) Continue this whilst the substance changes state (from solid to liquid)

Question 48

what is the specific heat capacity

Answer 48

the energy required to change the temperature of an object by one degree celcius per Kg of mass

Question 49

specific heat capacity formula

Answer 49

change in thermal energy = mass x specific heat capacity x change in temperature ΔQ = m × c × ΔT

Question 50

practical: investigate the specific heat capacity of materials including water and some solids

Answer 50

Place a polystrene cup on the digital balance and press 'zero' add 50g of water (50ml) add thermometer add an electrical heater into the water add a lid to the cup connect heater to power supply and add voltmeter and ammeter to circuit switch on power supply and start timer record values of amps and volts once water temp has raised by 20'c stop timer and power supply wait for water temp to stop increasing add into formula

Question 51

construction of an electro magnet

Answer 51

a soft iron core wrapped with coiled wire connected to a cell/battery

Question 52

what is the magnetic field pattern around a straight wire

Answer 52

field lines go in circles around the wire use the right hand rule to work out the direction that the field lines are going in

Question 53

what is the magnetic field pattern around a flat circular coil

Answer 53

it is circles around the wire

Question 54

what is the magnetic field pattern around a soleniod

Answer 54

the same as a bar magnet

Question 55

what happens to a charged particle when it moves parallel to the field lines

Answer 55

nothing it doesn't experience a force

Question 56

what happens to a charged particle when it moves perpendicular to the field lines

Answer 56

it will experience maxium force

Question 57

formula with input and output voltage, primary and secondary turns

Answer 57

input (primary) voltage / output (secondary) voltage = primary turns / secondary turns

Question 58

formula with input power and output power

Answer 58

input power = output power Vp x Ip = Vs x Is Vp is the primary voltage Ip is the primary current Vs is the secondary voltage Is is the secondary current

Question 59

structure of a transformer

Answer 59

A basic transformer consists of: A primary coil A secondary coil An iron core (as iron is magnetically soft)`

Question 60

how does a transformer work

Answer 60

An alternating current is supplied to the primary coil The current is continually changing direction This means it will produce a changing magnetic field around the primary coil The iron core is easily magnetised, so the changing magnetic field passes through it This changing field cuts through the secondary coil and induces a potential difference (induction) As the magnetic field is continually changing the potential difference induced will be alternating The alternating potential difference will have the same frequency as the alternating current supplied to the primary coil If the secondary coil is part of a complete circuit it will cause an alternating current to flow

Question 61

how does a transformer change the amount of voltage

Answer 61

by having different number of turns on the input and output side

Question 62

what is the use of step-up and step-down transformers in the large scale generation and transmission of electrical energy

Answer 62

as having a high current causes lots of resistance it is more efficient to transport electricity at high voltage with low current as it causes less resistance for the same amount of power and so less wasted energy. A step up transformer is used to increase the amount of voltage when it is being transported in the electricity pylons as this minimises lost energy. A step down transformer is then used to decrease the amount of voltage when the electricity is going into your home to a less dangerous amount that appliances can use.

Question 63

how can the brightness of a star at a standard distance be represented using absolute magnitude

Answer 63

as stars exist at very different distances from the earth so their brightness is represented on a standard scale (absolute magnitude) absolute magnitude compares stars as if they were all 10 parsecs (32.6 light years (3.1x10 ^ 17m) ) from earth the scale is centered at zero with bright stars having negative absolute magnitude and dimmer stars having positive absolute magnitudes

Question 64

what is apparent magnitude

Answer 64

The perceived brightness of a star as seen from Earth The apparent magnitude scale runs back to front: the brighter the star, the lower the magnitude the dimmer the star, the higher the magnitude

Question 65

how to draw a Hertzsprung-Russell diagra

Answer 65

luminosity (compared to the sun) goes on the y-axis and temperature (kelvin) on the x-axis luminosity increases in brightness as the y value increases temperature decreases is heat as x value increases (so starts at the hottest value) stars can also be displayed with colour where the hottest stars are blue and the coolest stars are red The key areas of the H-R diagram are: The brightest stars (high luminosity) are found near the top The dimmest stars (low luminosity) are found near the bottom The hottest stars (high temperature) are found towards the left The coolest stars (low temperature) are found towards the right

Question 66

where are stars found on H-R diagrams

Answer 66

The life cycle of a star can be shown on a Hertzsprung-Russell diagram The main features of the Hertzsprung-Russell diagram are: Most stars are found to lie on the main sequence. This is the band of stars going from top left to bottom right Below the main sequence (and slightly to the left) are the white dwarfs Above the main sequence on the right-hand side are the red giants Directly above the red giants are the red supergiants This means that The hottest, brightest stars are the largest main sequence stars, also called supergiant stars The coolest, brightest stars are red supergiants The hottest, dimmest stars are white dwarfs the coolest, dimmest stars are the smallest main sequence stars, also called red dwarfs

Question 67

equation with change in wavelength, velocity of a galaxy, speed of light and reference wavelength

Answer 67

change in wavelength = velocity of a galaxy ------------------------------------------------------------ reference wavelength = speed of light

Question 68

evidence for the big bang - expanding universe

Answer 68

the universe is constantly expanding - everywhere we look the galaxies are moving away from us and each other faster the fact that everything is moving away from each other and further away objects are moving faster, shows that the universe is expanding and so if you reverse that then everything gets closer and closer together until it all converges at one point, the big bang

Question 69

evidence for the big bang - red shift

Answer 69

when observing light spectrums from supernovas in other galaxies we see that the light has been redshifted showing that the galaxies are moving away from us as the wavelengths are increasing which shifts the colour to red. The further away galaxies are even more redshifted showing that the further away galaxies are moving even faster this shows the universe is expanding and started from an explosion as the universe is now moving out in all directions getting further and further from the source of the explosion

Question 70

evidence for the big bang - cosmic microwave background radiation

Answer 70

380,000 years after big bang protons and electrons combined to form neutral hydrogen atoms which radiated light. As the universe expanded and cooled, the wavelength of the visible light increased and shifted to microwaves. the CMBR has stretched during the expansion and cooling so the universe must have been smaller and hotter in the past. The CMBR is the same everywhere we look is evidence that all the points were touching during the big bang

Question 71

what is the doppler effect

Answer 71

when a source emitting waves is moving towards an observer, the waves are released closer together so the observer perceives the wavelength and frequency to have changed (wavelength decreases + frequency increases if the source if moving closer to the observer)