1. Physics Paper 2 Revision Version 1 some triple content to be added
Forces
Waves
Magnetism
Space (triple only)
Written exam –
1 hour 15 mins combined
1 hour 45 mins triple
100 marks
50% of your GCSE

2. Scalar and Vector quantities
Scalar quantities have size only
Vector quantities have size and direction
Contact and non-contact forces
Which are these? – push, pull, air resistance, magnetic, friction, electric field
Scalar
Vector
Distance, temperature, mass
Displacement, velocity, acceleration

3. Weight(N)=Mass(kg)x Gravitational field strength
Mass or Weight
Weight is the force of gravity acting on an object.
Weight is measured in Newtons.
Weight is the force calculated by:
Weight(N)=Mass(kg)x Gravitational field strength
(N/kg)
On Earth g=9.8N/kg
Or g=9.8m/s2
Recall and apply equation

4. Resultant Forces
When more than 1 force acts upon an object, a resultant force can be calculated.
This resultant force shows the overall affect of the force.
This shows us in which direction the force is accelerating in.
If the resultant force is zero:
A stationary object will not move.
An object in motion will stay the same velocity.

5. Resolving forces into vertical and horizontal components
Students should be able to use vector diagrams to illustrate resolution of forces, equilibrium and determine the resultant of twos forces using scale diagrams only

6. Work done 1 joule = 1 Newton-metre
When a force acts upon an object causing it to move a through a distance, energy is transferred and work is done. The amount of work done is equal to the amount of energy transferred. The amount of work done is calculated by: 2N 5m
Work done = 2N x 5m = 10J
Box moved from A to B A B
Work done (Joules, J) = Force applied (N) x distance moved (m)
1 joule = 1 Newton-metre
Work done against friction causes the temperature of the object to rise

7. Forces and elasticity e Work can also be done on other objects.
If you change the shape of an object by bending, stretching or compressing, then work done = elastic potential energy stored in the object, e.g. an elastic band.
To change the shape of an object, more than one force has to be applied.
Inelastic deformation results in permanent change or breaking of the object. Elastic deformation is when it can ‘bounce back’. e

8. Hooke’s Law
When a weight (force) is applied to a spring it extends. The amount it extends is proportional to the force added.(provided the limit of proportionality is not exceeded) It is governed by the equation:
Force(N) = spring constant (N/m) x extension(m)

9. Graph of Hooke’s Law
The spring constant can be determined from the gradient (slope of the line) on a force extension graph.
Limit of proportionality

10. For example: In the sample graph the section of the line chosen if for a force of 6N and an extension of 3m. k=F/e
k=6÷3=2N/m
Also marked on the graph is the limit of proportionality. This is the point at which the spring can still return to its original length. Beyond this point the spring can never go back to its original length/shape.

11. Moments, levers and gears – triple only
Also pressure and pressure differences
in fluids
Atmospheric pressure
Need to add some resources here

12. Speed Speed is a scalar quantity. s=vt
Speed = distance / time Units m/s
So distance travelled, s in m,
= speed, v x time, t in s
s=vt
Typical walking speed: 1.5 m/s
Typical running speed: 3 m/s
Typical cycling speed: 6 m/s
Car/bus 30mph = 13 m/s
Train 70 mph = 30m/s
Speed of sound 330 m/s
Recall and apply equation

13. Distance-time graphs How do you work out speed? Where is it fastest?
What is the average speed?
Is Bruce ever stationary?
What does the green line show?
Gradient = speed
If object is accelerating draw a tangent to curve and calculate gradient at that point

14. Velocity Velocity is speed in a given direction.
Velocity is a vector quantity
Circular motion at constant speed but the velocity is constantly changing
Circular motion is accelerated motion

15. Velocity-time graphs Where are the following: Acceleration?
Deceleration?
Constant Speed?
How would you work out distance travelled?
Acceleration = gradient
Distance travelled is area under the graph
Recall and apply equation
Acceleration = change in velocity
time
a = Δv / t units?

16. Working out acceleration
A velocity-time graph tells you how an objects velocity changes over a certain time.
This is the acceleration:

17. Uniform acceleration
Final velocity 2 – initial velocity 2 = 2 x acceleration x distance v2 - u2 = 2as where v is in m/s, a is in m/s2, s is in m You will be given this equation in the exam but you need to recognise when to use it and be able to substitute in and rearrange correctly!

18. Terminal velocity
An object falling through a fluid or gas will initially accelerate due to the force of gravity.
Eventually the force of gravity will be balanced by the up thrust of the liquid/gas; this makes the resultant force zero and the object will move at its terminal velocity (steady speed).
The faster the object falls the greater the frictional force that acts.

19. Terminal velocity – the skydiver

20. Newton’s First Law Inertia
When a vehicle travels at a steady speed, the resistive force are equal to the driving force
The velocity (speed or direction) of the vehicle will only change if there is a resultant force
If the resultant force acting on an object is zero – the object remains stationary, or continues moving at a constant speed.
Inertia
The tendency of an object to continue
in their state of rest
or uniform motion

21. Newton’s 2nd Law Force(N)=Mass(kg)x Acceleration(m/s2)
Acceleration of an object is proportional to force acting on it
acceleration ∝ force
Force(N)=Mass(kg)x Acceleration(m/s2)
Inertial Mass
A measure of how difficult it is to change the velocity (speed or direction) of an object
Defined as the ratio of force / acceleration.
You need to be able to give approximate answers
Recognise that the symbol for an approximate answer is
Recall and apply

22. Reaction Force Newton’s 3rd Law
Forces act in pairs. When 2 forces interact they are equal and opposite in direction e.g. a person exerts a force on the chair but the chair applies an equal force upwards on the person, a reaction force.

23. Forces and braking
When a vehicle travels at a steady speed the resistive forces balance the driving force.
b) The greater the speed of a vehicle the greater the braking force needed to stop it in a certain distance.
Large decelerations may cause brakes to overheat due to the work done by friction on the wheels increasing the temperature. .

24. Stopping distance = thinking distance + braking
How quickly a car can come to a stop depends on the car and the driver. The stopping distance is the thinking distance (which depends on the drivers reactions) and the braking distance (which depends on the car and road conditions).
Stopping distance = thinking distance + braking
distance

25. Thinking and braking distance
Typical reaction times vary from person to person in the range 0.2 – 0.9s
The thinking distance will be increased if the driver is tired, been drinking alcohol, been on drugs etc.
The braking distance will depend on the road surface, weather conditions and how well the car responds e.g. condition of brakes.

27. Momentum(kg m/s)=Mass(kg)xVelocity(m/s)
Momentum (has the symbol p) describes how much motion an object has. It is measured in kilogram metre per second (kg m/s). Like velocity, momentum has magnitude acting in a certain direction.
Momentum(kg m/s)=Mass(kg)xVelocity(m/s)

28. Conservation of momentum
In all situations, momentum is conserved, providing there are no external forces acting. For collisions, the momentum before the collision is equal to the momentum after the collision e.g. snooker balls.

29. Cannon momentum
Only triple science students will need to do calculations involving momentum

30. Change in Momentum – triple only
When a force acts on an object that is moving, or able to move, a change in momentum occurs.
Combine: F = m × a and a= (v−u) t
F = m (v-u) t = m∆v /∆t
where m∆v = change in momentum i.e. force equals the rate of change of momentum.
Application: car safety features

31. Collision Calculations: worked example
Moving trolley Stationary trolley 0.5kg 1.5kg 1.2m/s 0m/s They stick together after the impact

32. Worked example
Moving trolley (A) Stationary trolley (B) A’s momentum = 0.5kg x 1.2m/s B’s momentum = 0 = 0.6 kg m/s Total momentum = 0.6 kg m/s The momentum must remain the same after the impact.
What’s the unit?
What’s the unit?

33. Worked example
Moving trolleys stuck together (A + B) Total momentum = 0.5kg x 1.2m/s = 0.6 kg m/s Remember momentum = mass x velocity 𝑇𝑜𝑡𝑎𝑙 𝑚𝑜𝑚𝑒𝑛𝑡𝑢𝑚 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 =𝑡𝑜𝑡𝑎𝑙 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 So 0.6/2.0 = 0.3 m/s
What’s the unit?
What’s the unit?

34. Waves Wave speed (m/s) = frequency (Hertz) x wavelength (metres)
Longitudinal
Vibrations are parallel to the direction of energy transfer.
Compressions – where the lines are close together.
Rarefaction – where the lines are spread out.
Example – Sound waves
Waves transfer energy
Transverse
Vibrations are perpendicular to the direction of energy transfer
Electromagnetic waves are transverse.
Sound waves are longitudinal.
Mechanical waves can be either.
The particles in a wave move either horizontally or vertically only a short distance (vibrate)
E.g., ripples on water and sound in air it is the wave that moves and not the particles.
Wave speed (m/s) = frequency (Hertz) x wavelength (metres)
v = f x λ
Wave speed is the speed at which energy is transferred

35. Properties of Waves Identify: Amplitude wavelength
Frequency is the number of waves passing a point
each second
Period = 1 / frequency T – 1/f
where period T in s; frequency, f in Hertz Hz
Students need to be able to use this equation which will be given on the physics equation sheet

36. Reflection of Waves – triple only
You need to be able to show reflection at boundaries between materials
How waves are absorbed or transmitted at boundaries
draw ray diagrams to illustrate reflection
What are the effects of reflection, transmission and absorption at material interfaces

37. Sound Waves – triple only
You need to be able to describe sound waves and waves for detection and exploration

38. What is ultrasound?
The human ear can detect sound in the range of about 20Hz to 20000Hz.
Any sound with a frequency above 18000Hz is ultrasonic.
Ultrasonic waves are partly reflected at a boundary between two substances.
Ultrasonic waves are non-ionising.
Students need this information

39. How does ultrasound work?
Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object.
Students need this information
Words – depth, reflected, picture, medium

40. Using Ultrasound to Measure Distance
A pulse is emitted and the timer starts.
When the pulse hits the object, it is reflected.
The reflected pulse is detected and the timer stops.
Distance = speed x (time taken ÷ 2)

41. Electromagnetic Spectrum
Electromagnetic waves are transverse waves which form a continuous spectrum – the EM spectrum
Decreasing wavelength, increasing frequency, waves transfer more energy
All EM waves travel at the same speed in a vacuum.
Some of these EM waves can be used for communications:
Radio waves – TV and radio (these can be diffracted by mountains)
Microwaves – mobile phones and satellite TV, cooking food
Infrared – remote controls, cameras, cooking food, heaters
Visible light – photography, fibre optic communication
UV – sun tanning, energy efficient lamps
X-rays and gamma rays – medical imaging and treatments

42. Refraction
‘bending’ of a wave as it passes between two media of different densities
From a less dense medium to a more dense, the wave will bend towards the normal

43. Further properties of em waves
(HT) Radio waves arise from and can induce oscillations in an electrical circuit.
Gamma rays originate from changes in the nucleus of an atom.
Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer.
X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer

44. Lenses – triple only
Convex Lens

45. Visible Light – triple only
Key words:
Absorption
Transmission
Reflection
Transparent
Translucent
opaque

46. Black Body radiation All bodies emit radiation
The hotter the object, the more infra red radiation it emits
The perfect black body absorbs (and emits) ALL of the radiation falling on it
Temperature depends on the rate of absorption and reflection of radiation
The greenhouse
warms up in the
sun as it is
absorbing
more radiation
than it is
emitting

47. Magnetism The poles of a magnet have
the strongest magnetic forces. Like poles repel, unlike poles attract This is a non-contact force.
An induced magnet is a material that becomes magnetic when placed in a magnetic field but loses its magnetism quickly when removed

48. Magnetic Fields Direction of magnetic field is from North to South.
Magnetic materials are iron, steel, cobalt and nickel.

49. Electromagnetism
A current flowing through a wire generates a magnetic field.
The strength of the field depends on the current and distance from the wire.
Shaping the wire into a solenoid and adding an iron core increases the magnetic field and forms an electromagnet.
Triple students need to recognise and be able to explain diagrams of devices including electromagnets

50. Force on a conductor
When a wire carrying a current is placed in a magnetic field, the wire experiences a force. This is the motor effect.
Fleming’s Left Hand rule shows the
relative directions of current,
magnetic field and the force
on the wire:
F = B x I x ɭ
Force = magnetic flux density x current x length
F is force, N
B is magnetoc flux density, B in Tesla T
Current, I in Amps, A
Length, ɭ , in metres, m
Students will be given this equation but are expected to know how to apply

51. Electric Motors
A coil of wire carrying a current in a magnetic field tends to rotate. This is the basis of an electric motor.
Loudspeakers and headphones use this effect to convert variations in current to pressure vibrations of sound waves
Students need to be able to explain how the loudspeaker works

52. Transformers and the National Grid – triple only
If an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor, a potential difference is induced across the ends of the conductor. If the conductor is part of a complete circuit, a current is induced in the conductor. This is called the generator effect. An induced current generates a magnetic field that opposes the original change, either the movement of the conductor or the change in magnetic field. Students should be able to recall the factors that affect the size of the induced potential difference/induced current. Students should be able to recall the factors that affect the direction of the induced potential difference/induced current. Students should be able to apply the principles of the generator effect in a given context.

53. Uses of the generator effect – triple only
DC generator
AC generator
microphone

54. Transformers – triple only

55. Defining Key Terms
What is a ‘step-up’ transformer? What is a ‘step-down’ transformer?
Transformer that changes an alternating p.d. across the primary coil to a higher p.d. across the secondary coil.
Transformer that changes an alternating p.d. across the primary coil to a lower p.d. across the secondary coil.

56. Improving Efficiency
In the National Grid cables might have to cover up to a hundred miles from a power station.
Cables that long have very high resistance.
They heat up as the current flows through them which wastes energy.

57. The power station produces electricity at a voltage of 25,000 V and a current of 100 A.
Output power = 2.5 MW
Due to the high current, the cables will heat up and most of the electrical energy will be lost as heat.
Lost power = I2R = 0.5 MW
The total energy reaching homes and factories is only a 2.0 MW
At first, the National Grid was very inefficient.
The scientists came up with the solution ……
transformers

58. The solution is to reduce the current in the power lines in order to reduce the dissipated power.
Since P = I x V, reducing the current means increasing the voltage
230 V
132,000 V
25,000 V

59. The step up transformer steps up the voltage to 132,000 V (by a factor of 5.28). This causes the current to drop (by a factor of 5.28) to only 19A .
Lost power = I2R = 0.02 MW (very little heating effect)
The step down transformer steps down the voltage to a safe 230 V.
The current varies according to the appliances used.
The power station produces electricity at a voltage of 25,000 V and a current of 100 A.
input power = 2.5 MW

60. The Transformer Equation
This is based on a ratio.
Vp = primary p.d. in volts, V
Vs = secondary p.d. in volts, V
Np = number of turns on primary coil
Ns = number of turns on secondary coil
Example:
A transformer is used to power some coloured lights. There are 30 turns on the secondary coil and 600 on the primary coil. The primary coil is connected to the mains (230 V a.c.) What is the voltage across the secondary coil?
Answer:
Vp ÷ Vs = Np ÷ Ns
230 ÷ ? = 600 ÷ 30
230 ÷ ? = 20
? = 230 ÷ 20 = 11.5 V
Vp ÷ Vs = Np ÷ Ns
Left click will reveal answer

61. Vs x Is = Vp x Ip (USE and APPLY)
Power input and output
Vs x Is = Vp x Ip (USE and APPLY)
Vs x Is is the power output (secondary coil)
Vp x Ip is the power input (primary coil)
Power input and output are measured in watts, W.
Vs x Is = Vp x Ip
x ? = 50 x 100
x ? = 5 000
? = ÷ = A
Example:
If primary voltage is 50 V and current is 100 A, given the output voltage is V, what is the current?

62. Space Physics =triple only
The milky way galaxy is home to our solar system, which comprises:
One star – the Sun
Eight planets
Dwarf planets
Natural satellites (moons)

63. Life cycle of a star: sbsd Cloud of gas and dust (nebula)
Drawn together by gravity causing fusion reactions
sbsd
Star reaches a balance beween gravitational collapse of star due to its mass and expansion due to fusion reactions
Fusion reactions in stars produce all naturally occurring elements. The explosion of a supernova distributes them around the galaxy

64. Black Dwarf
Main Sequence Stars

65. Orbital motion, natural and artificial satellites – triple only
Similarities and differences between planets, moons and artificial satellites
Force of gravity provides the changing velocity for circular orbits but speed is constant
If the speed changes for a circular orbit, then the radius of the orbit must change

66. Triple only -Red-shift
Doppler  an object making a sound is moving away from you, the sound waves stretch out  wavelength increases, frequency decreases
Doppler can also be applied to light, but the object emitting the light needs to be moving very fast and huge distances  this is called Red-shift
Absorption spectra:
These show which colours of light are absorbed by, for example, the atmosphere of a planet or the contents of a galaxy. The absorbed light is shown by dark lines on a colour spectrum. For a galaxy moving away from us, these lines are shifted towards the red end of the spectrum.
Red-shift is one piece of evidence for the theory that the universe started through a very rapid expansion (the Big Bang) and is continuing to expand (CMBR is another piece of evidence).
The faster a star or galaxy is moving away from us, the bigger the red-shift will be.
There is still much about the Universe that is not understood, for example, dark matter and dark energy

67. Triple Only Big Bang Theory
The Big Bang theory states that…
Everything in the known Universe was contained at a very hot, very dense initial point. A rapid expansion took place around 13.7 billion years ago in which space, time and all matter were created. There are 2 key pieces of evidence for this theory – CMBR and Red-shift.
OTHER THEORIES
There are other theories for the origins of the Universe. Steady State theory suggests that the Universe has always been huge and is expanding because matter is entering the Universe through white holes. There is very little evidence for this theory.
Red-shift is another piece of evidence that the Universe is expanding because it shows us that galaxies are moving away from each other.

68. Tips from the Examiners
Always include the correct units with your answer.
Watch out for time given in minutes or hours when it should be in seconds, mass in grams, kJ, kW etc.
You will need to rearrange some equations – practise!
Read questions and the information given to you carefully so that your answer matches what is being asked.

69. What went badly last summer
Forces – identifying different forces and the resultant force
Explaining why different components are used in a circuit
Explaining how temperature affects resistance
Fission – using fission to generate electricity; drawing a diagram of a chain reaction
Mains electricity – structure of a plug and a cable; definitions of a.c. and d.c.