1. Physics 2

2. Distance Distance-Time Graphs Gradient = Speed
Flat sections are stationary
Straight = steady speed
Curves= acceleration or deceleration

3. Velocity and Acceleration
Acceleration is how quickly velocity is changing
Acceleration=Change in Velocity/Time Taken
Velocity-Time Graphs
Gradient = Acceleration
Flat sections = steady speed
Area under the graph represents distance
Curve is change in acceleration

4. Weight
MASS is the “stuff” inside, whereas WEIGHT is the force due to gravity
Weight = Mass x Gravitational Field Strength
Earths GFS is 10N/Kg

5. Resultant Forces It is the overall FORCE
The overall effect of forces which will decide the motion of an object
If two forces are acting in the same direction, the resultant force is the sum of those two
If two forces are acting along the same line, then the resultant force is found by subtracting them

6. Resultant Force =1600N
Pushing Force =600N
Driving force =1000N
Resultant Force =400N
Driving force =1000N
Friction =600N

7. Acceleration If the resultant force in 0 the object is stationary
It there is no resultant force on a moving object, then it will carry on moving with constant velocity
If there is an resultant force, then the object will accelerate in the direction of the force
That is until the force equal out again

8. Force = Mass x Acceleration Or Acceleration = Force / Mass
When two object interact, the forces they put (exert) upon each other are equal and opposite
This is called a reaction force, so if you push against something it will push back against you with equal force

9. Friction It acts against movement
If you travel at a steady speed, the driving force needs to equal the frictional force
Streamlining reduces drag or air resistance
Drag increases as speed increases, as you accelerate you hit more air particles with more force. This created more drag

10. Terminal Velocity
When an object first falls, gravity (weight) has more force than frictional forces
This causes the object to accelerate downwards
As the speed increases, so does the drag
This reduces the acceleration
Weight can not get any bigger, so you reach terminal velocity (fall at a steady speed)

11. Stopping Distance Thinking Distance
Faster you are going = Further you will go
Your Reactions- Tiredness, drugs, alcohol, bad visibility and distractions
Braking Distance
The Car- the condition of Tyres and condition of Brakes
The Road- road surface and weather condition

12. Stopping Dis. = Thinking Dis. + Braking Dis.
So this shows that thinking distance is directionally proportional but braking distance is squarely proportional 9m
14m
30 mph
15m
38m
50 mph
21m
75m
70 mph
Thinking Braking Distance Distance
Stopping Dis. = Thinking Dis. + Braking Dis.

13. Work Done To move an object energy has to be transferred
The energy can be used usefully i.e. To move something or wastefully i.e. Friction
Work Done= Force x Distance Moved

14. Gravitational Potential Energy
When an object is lifted vertically work is done against the force of gravity. This is transferred into gravitational potential energy (GPE)
GPE= Mass x Height x GFS (gravitational field strength)
The Earth has a GFS of 10N/Kg

15. Kinetic Energy Any thing that moves has kinetic energy
Kinetic Energy = ½ Mass x Speed²
Moving car has lots of KE so to slow it down energy is lost i.e. Heat energy
Work done = KE
F x d = ½ mv²
Falling objects have the potential energy lost and they gain kinetic energy

16. Elasticity Apply a force = Stretch the Object
Work done is stored as ELASTIC POTENTIAL ENERGY
Then its goes back to its original shape releasing the energy as KINETIC ENERGY

17. Extension of Spring is DIRECTIONALLY PROPORTIONAL to the force applied
Force = K (spring constant) x energy
There is a limit to a springs elasticity, it is normal until it reaches its maximum force
Past this point the spring will not return to its original shape

18. Power It is the rate of doing work Power = Work Done / Time Taken
Measured in Watts, which means 1 Watt is 1 joule of energy transferred every second

19. Momentum It’s a property of a moving object Momentum = Mass x Velocity
Also P before = P after
Momentum is a vector, so has direction
When a force acts upon an object it changes its momentum
The bigger the force the faster the change of momentum

20. Car Safety
Brakes transform the kinetic energy of the car into thermal energy on the road
Regenerative brakes don’t transform into heat the transform into electrical energy
Big change in Momentum in a short time = MASSIVE

21. End of First Half

22. Static Electricity
It is created when two object rub against each other and either lose or gain electrons
Like charges repel, so if hair had been charged then the hair would separate because their like charges repel each other
However these charges can be easily lost through a conductor

23. Current and Voltage Current is the rate of flow of charge
Current= Charge / Time
The Potential Difference is the work done per coulomb of charge
Voltage = Work Done / Charge

24. Circuits

25. Resistance
Current through a resistor (at constant temp.) is directionally proportional to Voltage The higher the resistance the higher the potential difference However in a normal filament lamp the temperature of the filament increases this causes the curve This is a Diode. The current will only flow in one direction. The diode has a very high resistance in the opposite direction

26. Series All or nothing, if one component breaks ao does the circuit
Potential difference is shared out, so in 23 fairy-lights on the mains electricity they all have a voltage of 10V
Current is the same everywhere
And the Resistance builds/adds up, 5 bulbs with 10Ω so the circuit has 50Ω

27. Parallel Things can be switched off separately
Voltage is the same across all components
However current is shared between each branch. The current going in is the same as going out, but the components have different currents going across them

28. Mains Electricity Supplied in AC Has 230V And has frequency of 50Hz
It can be shown on an oscilloscope

29. Electricity in the Home
Hazards: Long Cables; Frayed cables; damaged plugs; too many plugs in 1 socket; water near sockets The wires: Live wire carries the alternating current; Neutral has 0V and Earth is attached to metal casing

30. BROWN I G H T
BLUE E F T

31. Fuses and Earthing
Fault in the LIVE WIRE causes it to touch the metal case
This causes a larger current to flow through the circuit
This surge cause the FUSE to MELT
This cuts of the live supply and breaks the circuit, THUS saving the appliance and the user

32. Live wire touches the metal casing
Big Surge of Electricity to earth
Fault in the Live Wire
The Fuse melts/blows
The appliance is SAFE

33. Energy and Power
All resistors produce heat when a current flows through them. The more current the more heat
To be energy efficient they have to transfer more of their total electrical energy to a useful source
Energy Transferred= Power Rating x Time

34. Atomic Structure- Rutherford
In 1909 Rutherford fired alpha particles at gold foil to discover more about particles
He found most went straight through, this shows particles are mostly empty space
Some came straight back, the shows that most of the mass is concentration in a central nucleus
Some were deflected, this shows the nucleus is positive and there must be negative electrons not in the nucleus

35. Radiation
Isotopes are atoms of the same element but are slightly different, they have the same number of protons but different numbers of neutrons
Radioactivity is entirely random, it comes from an unstable and decaying nuclei. This emits alpha, beta or gamma radiation
Background radiation comes from: naturally unstable isotopes like rocks and food; space like cosmic rays; Man-made places like weapons and medicine and power-stations

36. Types of Radiation
Alpha radiation is a helium nucleus, so two protons and two neutrons. Can’t penetrate much but because of its size it’s strongly ionising (bash into atoms and knock electrons off of them) Beta radiation is an electron which is emitted when a neutron turns into a proton. Can go through some things and is mildly ionising Gamma radiation is an ray. This penetrates everything but is weakly ionising.

37. Radiation Safety
Radiation damage depend on the type of radiation and how long you were exposed
Alpha particles are deflected slightly by magnetic field but beta particles are extremely deflected by the magnetic field
Granite release radon gas which can be trapped in peoples houses
Nuclear industry workers wear protective clothing and face masks and have radiation badges
Radiographers work behind lead screens and wear lead aprons

38. Half-Life
Half life is the AVERAGE TIME it takes for the NUMBER OF NUCLEI in a radioactive isotope to HALVE
Radioactivity never stops, there will always be some activity, so its hard to measure
Short half life means lots of nuclei decay quickly, activity falls quickly

39. -1 Half Life-
-1 Half Life-
-1 Half Life-

40. Uses of Radiation
Smoke detectors- alpha particles make and circuit and smoke breaks the circuit, making the alarm go off
Sterilisation- Gamma rays are used to kill bacteria on food or medical equipment, without harming them
Radiotherapy- gamma is fired at a cancer to kill all of those cells, but damage is done
Tracers- beta or gamma sources are put into someone and an external detector says where most of the radiation is

41. Damage of Radioactivity
Large amounts of radiation kill cells and leave you with radiation sickness, but nothing else
Small amounts cause minor damage to cells without killing them. They then mutant and divide uncontrollably, this is a cancer
Alpha is very harmful inside the body because it damages a very localised area
Beta and gamma are dangerous outside the body because they can penetrate the skin

42. Nuclear Fission
This is what happens in nuclear power stations and nuclear bombs
An Neutron had to be absorbed by an unstable nuclei
This creates two new smaller nuclei and releases more neutron, this makes a chain reaction
This gives out a lot of energy

43. Nuclear Fusion
This is where two small nuclei join to create a larger nucleus and energy
Fusion doesn’t leave a lot of radioactive waste and there is a bounty of fuel (hydrogen)
It can only happen at really high temperatures
You need at strong magnetic force to hold the pressure and heat 2 1 1 3 2 H H He + + 
ENERGY

44. Life Cycle of Stars
Red Giant- hydrogen has run out and it was a small star OR
Main Sequence star- long stable period where outward pressure is equal to the force of gravity (the sun) but this can’t last forever
Nebula- The nursery for Stars. Clouds of Dust and gas start to form. Gravity makes it spiral and form a Protostar
Protostar- Gravity is turned into heat. The temp is then high enough for nucleur fusion to start. This gives out light, star
Red SuperGiant- Hydrogen has run out but it was a big star

45. Red Giant
White Dwarf- This is what’s left after the red giant. It is a hot solid, dense core. When it cools down it becomes a Black Dwarf
Red Giant- small star make this. It is unstable so ejects its outer layer of dust and gas.
Planetary Nebula- This is the outer layer of duct and gas.

46. Red SuperGiant
Neutron Star- What is left of the supernova is a dense core. This is an neutron star OR
Black Hole- If the star is big enough the remains of the supernova will form a black hole
Supernova- This is the explosion of the Red SuperGiant. It forms elements heavier than iron and spreads them out into the universe creating new planets and new stars
Red SuperGiant- This is made from large stars. They glow more brightly because they do more fusion, so they expand