Physics

1. Physics Edexcel International GCSE in Physics (4PH0) First examination June 2013

2. Forces and motion • Units • Movement and position • Forces, movement, shape and momentum • Astronomy

3. Units 1.1 use the following units: kilogram (kg), meter (m), meter/second (m/s), meter/second2 (m/s2), newton (N), second (s), newton per kilogram (N/kg), kilogram meter/second (kg m/s) • Kilogram (kg) is for mass • Meter (m) is for distance • Meter / second (m/s) is for speed or velocity • Newton (N) is for force • Second (s) is for time • Newton per kilogram (N/kg) is for acceleration (same as m/s2) • Kilogram meter / second (kg m/s) is for momentum

4. Movement and position 1.2 plot and interpret distance-time graphs • Gradient or slope gives speed. • Straight lines mean constant speed. Curved lines mean acceleration or deceleration. • Flat lines mean stationary. • Red line shows that the object is moving forward at a constant speed. • Green line shows that it is stationary. • Blue line shows that the object is moving backward at a constant faster speed. • The dotted line is to show the gradient calculations to calculate the speed. Distance Time

5. Movement and position 1.3 know and use the relationship between average speed, distance moved and time: • Average speed = distance moved / time taken 1.4 describe experiments to investigate the motion of everyday objects such as toy cars or tennis balls • Experimenting with rolling tennis balls and toy cars, measuring the distance and time taken and working out the average speed. • e.g. A toy car is pushed, it moves 4 meters in 2 seconds. • Distance moved: 4m • Time taken: 2s • Calculation: Speed = 4 / 2 • Speed = 2 m/s

6. Movement and position 1.5 know and use the relationship between acceleration, velocity and time: • Acceleration = change in velocity / time taken 1.6 plot and interpret velocity-time graphs • Gradient or slope gives acceleration. • Straight lines mean constant acceleration. Curved lines mean increasing or decreasing acceleration / deceleration. • Flat lines mean constant speed. Velocity Time

7. Movement and position • Red line shows that the object is accelerating constantly. • Green line shows that the object is at a constant speed. • Blue line shows that the object is decelerating constantly. 1.7 determine acceleration from the gradient of a velocity-time graph • Acceleration is determined from the gradient or slope of the graph. • The dotted line shows the gradient calculations to calculate acceleration. 1.8 determine the distance travelled from the area between a velocity-time graph and the time axis. • The area between the line and the axis shows the distance travelled during the motion.

8. Forces, movement, shape and momentum 1.9 describe the effects of forces between bodies such as changes in speed, shape or direction • When an object is stationary or moving at a constant speed, the forces are balanced. • In the case of the car, the forward and backward forces are equal when the car is at a constant speed. • When the forward forces are greater than the backward forces, the car accelerates. • When the backward forces are greater than the forward forces, the car decelerates. Or, it will change the direction in which the car is going eventually.

9. Forces, movement, shape and momentum 1.10 identify different types of force such as gravitational or electrostatic • Weight: the force that acts on a body because of gravity • Friction: the force that opposes motion • Air resistance: friction between an object and the air • Viscous drag: similar to air resistance, but between an object and a liquid • Upthrust: the upward force that liquids and gases exert on objects • Magnetic: the forces that magnets exert on other magnets or ferrous materials • Electrostatic: the force between electrically charged objects • Normal reaction: the name for the contact force that acts on an object pressing down on another. • Tension: in strings cable, ropes that are being stretched.

10. Forces, movement, shape and momentum 1.11 distinguish between vector and scalar quantities • Scalar quantities have only one measurement: • Speed • Distance • Temperature • Vector quantities have a direction: • Displacement (distance in a specified direction) • Velocity (speed in a specified direction) 1.12 understand that force is a vector quantity • Force has a direction

11. Forces, movement, shape and momentum 1.13 find the resultant force of forces that act along a line • A resultant force is the consequence of unbalanced forces along a line. • 500 N forwards • 200 N backwards • 500 – 200 = 300 • The resultant force is 300 N forwards 1.14 understand that friction is a force that opposes motion • Friction opposes motion because of the abrasion between the two surfaces. 200N 500N

12. Forces, movement, shape and momentum 1.15 know and use the relationship between unbalanced force, mass and acceleration: • Force = mass X acceleration 1.16 know and use the relationship between weight, mass and g: • Weight = mass X gravitational field strength (g) 1.17 describe the forces acting on falling objects and explain why falling objects reach a terminal velocity • As the velocity downwards increases, the air resistance increases. This occurs until the air resistance force is equal to the weight force. When the two forces are balanced, the object reaches a constant speed and this is called terminal velocity.

13. Forces, movement, shape and momentum 1.18 describe experiments to investigate the forces acting on falling objects, such as sycamore seeds or parachutes • When a man jumps off a plane, his weight causes him to accelerate downwards, this continues until the air resistance equals the force of his weight and he reaches a terminal velocity. • When he opens his parachute, he decelerates drastically because the air resistance force is greater than his weight. As he slows down, the air resistance decreases and gradually another terminal velocity is reached. 1.19 describe the factors affecting vehicle stopping distance including speed, mass, road condition and reaction time • Thinking distance: intoxication, poor visibility, tiredness • Braking distance: poor tires, road surface

14. Forces, movement, shape and momentum 1.20 know and use the relationship between momentum, mass and velocity: • Momentum = mass X velocity 1.21 use the idea of momentum to explain safety features • Newton’s second law is force = change in momentum / time taken • The change in momentum is fixed by the speed the car is traveling at and the mass of the car and contents. • Therefore if the equation is rearranged as force X time = change in momentum, force and time is inversely proportional. • It is vital to increase time for the car to come to rest to minimalize the force. Therefore, crumple zones and airbags are used to increase the time.

15. Forces, movement, shape and momentum 1.22 use the conservation of momentum to calculate the mass, velocity or momentum of objects • Total momentum of the two bodies before collision = total momentum of the two bodies after collision • Elastic collision is which no energy is lost (no energy being converted into heat or sound) • Inelastic collision is when the colliding objects do not rebound at all • A small pellet of mass 0.01 kg travelling at 30 m/s towards a stationary wheeled block with a mass of 0.19 kg. • Momentum before collision = 0.01 kg X 30 m/s = 0.3 kg m/s • Momentum after the collision = (0.19 kg + 0.01 kg) X v = 0.2 X v = 0.3 kg m/s • v is 1.5 m/s

16. Forces, movement, shape and momentum 1.24 demonstrate an understanding of Newton’s third law • Newton’s third law is for every action there is a equal and opposite reaction. 1.25 know and use the relationship between the moment of a force and its distance from the pivot: • Moment = force × perpendicular distance from the pivot 1.26 recall that the weight of a body acts through its center of gravity • The whole weight of an object acts through one point of the object called its center of gravity. • e.g. If a shape is suspended from a point, so that it can turn, it will come to rest with the center of gravity of the object immediately below the point from which it is suspended.

17. Forces, movement shape and momentum 1.27 know and use the principle of moments for a simple system of parallel forces acting in one plane • Sum of clockwise moments = sum of anticlockwise movement • 400N X 1.5 m = 300N x d m • d = 2m d m 1.5 m 400N 300N

18. Forces, movement, shape and momentum 1.28 understand that the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam • When the object is placed in the middle of the beam, the upward forces of the support beams are equal. However, when the object is placed closer to one side, the closer support beam will have a higher upward force, and the further one will have a lower upward force. 1.29 describe experiments to investigate how extension varies with applied force for helical springs, metal wires and rubber bands • Hanging known masses under the spring or rubber band and measuring the length. • The extension of a spring is directly proportional to the force pulling on it until it reaches a elastic limit. • After it is extended beyond the elastic limit, it does not return to its original length. • A rubber band returns to its original length when the stretching force is removed, provided it is not stretched beyond the breaking point.

19. Forces, movement, shape and momentum 1.30 understand that the initial linear region of a force-extension graph is associated with Hooke’s law • The initial linear region of a force-extension graph follows Hooke’s law. The increase in length of a spring is directly proportional to the force pulling on it. 1.31 describe elastic behavior as the ability of a material to recover its original shape after the forces causing deformation have been removed. • It returns to its original form, unless it has been stretched beyond its elastic point. • In this case, it returns to a lengthened form.

20. Astronomy 1.32 understand gravitational field strength, g, and recall that it is different on other planets and the moon from that on the Earth • The strength of the gravity depends on: • The size of the masses involved. • The distance between the masses. 1.33 explain that gravitational force: • causes moons to orbit planets • causes the planets to orbit the sun • causes artificial satellites to orbit the Earth • causes comets to orbit the sun • Gravity is the force that keeps the moon in orbit around the earth and the moon of other planets in our solar system in their orbits.

21. Astronomy 1.34 describe the differences in the orbits of comets, moons and planets • Planets orbit the sun in a spherical path. • Comets orbit the sun in an elliptical path. • Moons orbit the planet in an elliptical path. 1.35 use the relationship between orbital speed, orbital radius and time period: • Orbital speed = 2 X pi X orbital radius / time period 1.36 understand that: • the universe is a large collection of billions of galaxies • a galaxy is a large collection of billions of stars • our solar system is in the Milky Way galaxy.

22. Electricity • Units • Mains electricity • Energy and potential difference in circuits • Electric charge

23. Units 2.1 use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V), watt (W) • Ampere (A) is for current • Coulomb (C) is for charge • Joule (J) is for energy • Ohm (Ω) is for resistance • Second (s) is for time • Volt (V) is for voltage • Watt (W) is for power

24. Mains electricity 2.2 understand and identify the hazards of electricity including frayed cables, long cables, damaged plugs, water around sockets, and pushing metal objects into sockets • Frayed cables can expose live wires. • Long cables are more likely to get damaged or trip people up. • Damaged plugs or insulating casing may expose live wires. • Water around electric sockets. • Pushing metal objects into mains sockets. 2.3 understand the uses of insulation, double insulation, earthing, fuses and circuit breakers in a range of domestic appliances • Insulation: All mains wiring is double insulated with two layers of insulation. This prevents separate conductors (live, neutral and earth) from touching. • Double Insulated: As well as the wiring being insulated, the outer casing of the appliance is also made of an insulating material. • Earthing: Provides a low resistance path for the current in the event of a fault, it ensure that the outer casing is held at 0V.

25. Mains electricity • Fuses are fitted into plugs, they contain a wire designed to melt when a specified current size is exceeded, cutting off the live wire. • Circuit breakers are now more commonly used to replace fuses as they are magnetically operated and they can be reset by pressing a button. 2.5 know and use the relationship: power = current × voltage, and apply the relationship to the selection of appropriate fuses • Power = current X voltage • e.g. An electric drill with a power rating of 750W is designed to run from the 230V mains supply. • 750W / 230V = 3.26A • The threshold of the fuse has to be larger than 3.26A. 2.6 use the relationship between energy transferred, current, voltage and time: • Energy transferred = current X voltage Xtime

26. Mains electricity 2.7 understand the difference between mains electricity being alternating current (a.c.) and direct current (D.C.) being supplied by a cell or battery. • Direct current is when the electricity flows in one direction only. • Alternating current is when the current changes continuously, with electricity flowing one direction then the other.

27. Energy and potential difference in circuits 2.8 explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting • Parallel circuits are appropriate for domestic lighting because if one outlet is disconnected, the others will continue working. • Series circuits are appropriate for decorative lighting because the voltage in each lamp is lower. However, the lights all go out if one bulb fails.

28. Energy and potential difference in circuits • Series Circuit • The same current flows through all the components. • If the current was 2A, it would be 2A all around the circuit. • The voltage is split equally between all the components, but only if they are all identical. • If the battery was 4.5V, each of the lamps would have a voltage of 1.5 each.

29. Energy and potential difference in circuits • Parallel Circuit • The current is split at the junction, it splits equally if the lamps are identical. • If the current is 4A at the point A, the current will be 2A at point B and C. • The voltage acts as if the battery supplied each of the bulbs individually. • If the battery was 9V, bulb B and bulb C would each have a voltage of 9V. • Each parallel B and C acts as their own series circuit, thus if more bulbs were added the voltage would split between them and the current would be less on that parallel as there is more resistance. A C B

30. Energy and potential difference in circuits 2.9 understand that the current in a series circuit depends on the applied voltage and the number and nature of other components • If the number of components is constant, an increase in voltage would induce an increase in current. • If the voltage is constant, an increase in the number of components would induce a decrease in current. • This is because each component has its own resistance. The more resistance there is, the lower the current. • Ohm’s law is that current is proportional to voltage if the resistance is constant.

31. Energy and potential difference in circuits 2.10 describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can be investigated experimentally • This variable can be investigated experimentally by using a variable resistor, ammeter, and voltmeter connected like this. • The variable resistor is so that the voltage can be changed. • Remember that the voltmeter is connected in parallel. • Resistors and wires obey Ohm’s law, which means the resistance is constant and the voltage and current is proportional. This is a straight line on the current-voltage graph. • Filament lamps get very hot and the resistance of a metal increases with temperature. The resistance increases as the voltage increases. This is a straight line then plateauing line on the current-voltage graph. • Diodes have a very large resistance when the voltage is applied in the wrong direction. This is shown by the horizontal line when the voltage is negative (showing the wrong direction).

32. Energy and potential difference in circuits 2.11 describe the qualitative effect of changing resistance on the current in a circuit • Increasing the resistance would lower the current. • Decreasing the resistance would increase the current. 2.12 describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature • Light Dependent Resistor: • More light  Less resistance • Less light  More resistance • Thermistor: • More heat  Less resistance • Less heat  More resistance

33. Energy and potential difference in circuits 2.13 know that lamps and LEDs can be used to indicate the presence of a current in a circuit • When a lamp is on, it shows that the flow of electricity is present. 2.14 know and use the relationship between voltage, current and resistance: • Voltage = current × resistance 2.15 understand that current is the rate of flow of charge • Current is how fast the electricity flows. 2.16 know and use the relationship between charge, current and time: • Charge = current X time

34. Energy and potential difference in circuits 2.17 know that electric current in solid metallic conductors is a flow of negatively charged electrons • The electrons are negatively charged therefore they are repelled from the negative terminal and attracted towards the positive terminal. Thus they flow from negative  positive. This is the electron flow. • The conventional current is from positive  negative. 2.18 understand that: • voltage is the energy transferred per unit charge passed • the volt is a joule per coulomb. • The equation linking energy transferred, current, voltage and time is energy transferred = current X voltage X time. • Current X time = charge • Therefore, energy transferred = charge X voltage (J = CV) • Therefore, V = J / C

35. Electrical charge 2.19 identify common materials which are electrical conductors or insulators, including metals and plastics • Materials that conduct electricity are conductors. • Usually metallic: copper, silver, gold. • Materials that cannot conduct electricity are insulators • Usually non-metallic: rubber, glass, plastics 2.20 describe experiments to investigate how insulating materials can be charged by friction • When you rub two different insulators together they become electrically charged. • This is because electrons in one of the insulators is ripped off its surface, and thus becoming positively charged. The other insulator gains the electrons, and thus becoming negatively charged. • Charged insulators can attract small uncharged objects such as pieces of paper. • Polythene and clear acetate rods can be charged on a dry day by rubbing them with a dry cloth.

36. Electrical charge 2.21 explain that positive and negative electrostatic charges are produced on materials by the loss and gain of electrons • Electrons have a negative charge. • The gain of electrons would induce a negative electrostatic charge. • The loss of electrons would induce a positive electrostatic charge. 2.22 understand that there are forces of attraction between unlike charges and forces of repulsion between like charges • Positive and negative electrostatic charges attract to each other. • Like charges repel each other. 2.23 explain electrostatic phenomena in terms of the movement of electrons • This is because electrons in one of the insulators is ripped off its surface, and thus becoming positively charged. The other insulator gains the electrons, and thus becoming negatively charged.

37. Electrical charge 2.24 explain the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers • Fuelling aircraft and tankers: When fuelling aircraft and tanker, a static charge may be built up. It is important to earth the plane or tanker to discharge the static charge, as a spark could cause a fire or explosion. • Handling computer components: It is important that there is no static charge on the worker as being static can easily destroy these components. • Electric shocks: Cars become charge with static electricity, and can give a shock when someone touches it.

38. Electric charge 2.25 explain some uses of electrostatic charges, e.g. in photocopiers and inkjet printers • Inkjet printers: Charging parts of the paper negatively using a laser, then the oppositely charged toner is attracted to the negatively charged parts and thus forms an image which is pressed by a fuser. • Photocopier: A statically charged drum is exposed to light, reflected from the document. The light discharges all the parts except for where the dark print does not reflect. The charge parts of the drum attract the toner which is then transferred to printer paper. • Paint spraying: The tiny droplets of paint are given a static charge and the object to be painted is connected to a supply of opposite charge. This causes the paint droplets to be attracted, and the amount of wasted paint is drastically reduced. • Electrostatic precipitators: Small particles of soot and other dust produced in combustion are given a small static charge and are then passed through a highly charged grid which attracts dust particles stopping them from escaping.

39. Waves • Units • Properties of waves • The electromagnetic spectrum • Light and sound

40. Units 3.1 use the following units: degree (o), hertz (Hz), meter (m), meter/second (m/s), second (s) • Degree (o) is for angle • Hertz (Hz) is for frequency • Meter (m) is for distance or length • Meter / second (m/s) is for speed or velocity • Second (s) is for time

41. Properties of waves 3.2 understand the difference between longitudinal and transverse waves and describe experiments to show longitudinal and transverse waves in, for example, ropes, springs and water • Mechanical waves need a material medium to travel through. • Transverse : The medium moves perpendicular to the direction of the motion of the wave. • Ripples in a pond • Longitudinal: The medium moves parallel to the direction of the motion of the wave. • Sound wave • To show the properties of each wave, a slinky (spring) can be used: • Moving the slinky quickly vertically induces a transverse wave. • Moving the slinky quickly forwards and backwards induces a longitudinal wave.

42. Properties of waves 3.3 define amplitude, frequency, wavelength and period of a wave • Amplitude: is the maximum displacement of a part of the medium from its rest position. • Wavelength is the distance between corresponding points in the wave – one crest to the next crest in a transverse wave. • Period of is the time for one complete cycle of the waveform. • Frequency is the number of cycles of the waveform per second. 3.4 understand that waves transfer energy and information without transferring matter • Waves transfer energy without transferring matter. 3.5 know and use the relationship between the speed, frequency and wavelength of a wave: • Wave speed = frequency X wavelength • The symbol of wavelength is λ.

43. Properties of waves 3.6 use the relationship between frequency and time period: • Frequency = 1 / time period 3.7 use the above relationships in different contexts including sound waves and electromagnetic waves • All electromagnetic waves travel at the same speed of 300,000,000 m/s in a vacuum. • Radio station A transmits radio waves with wavelength 200m. • Radio station B transmits radio waves with wavelength 300m. • Use the wave equation to calculate the frequencies of the radio waves. • Wave speed = frequency X wavelength or frequency = wave speed / wavelength • Radio station A: 1,500,000 Hz • Radio station B: 1,000,000 Hz

44. Properties of waves 3.8 understand that waves can be diffracted when they pass an edge • Diffraction is the spreading of waves as they pass by edges of obstacles. • It stems from the theory that one can hear a sound around the corner. 3.9 understand that waves can be diffracted through gaps, and that the extent of diffraction depends on the wavelength and the physical dimension of the gap. • The closer the width of the gap and the wavelength, the greater the effect.

45. The electromagnetic spectrum 3.10 understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space • Electromagnetic waves are transverse. • They do not use a material medium. • All travel at the 300,000,000 m/s through a vacuum 3.11 identify the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colors of the visible spectrum • Radio waves  Microwave  Infrared  Visible  Ultraviolet  X-Ray  Gamma Ray • Red  Orange  Yellow  Green  Blue  Indigo Violet • Increasing frequency  Increasing wavelength • Since speed is constant, frequency and wavelength must be inversely proportional.

46. The electromagnetic spectrum 3.12 explain some of the uses of electromagnetic radiations, including: • Radio waves: broadcasting and communications • Microwaves: cooking and satellite transmissions • Infrared: heaters and night vision equipment • Visible light: optical fibers and photography • Ultraviolet: fluorescent lamps • X-rays: observing the internal structure of objects and materials and medical applications • Gamma rays: sterilizing food and medical equipment

47. The electromagnetic spectrum 3.13 understand the detrimental effects of excessive exposure of the human body to electromagnetic waves, including: • Microwaves: internal heating of body tissue • Infrared: skin burns • Ultraviolet: damage to surface cells and blindness • Gamma rays: cancer, mutation

48. Light and sound 3.14 understand that light waves are transverse waves which can be reflected, refracted and diffracted • Light waves are transverse waves which can be: • Reflected • Refracted • Diffracted 3.15 use the law of reflection (the angle of incidence equals the angle of reflection) • Angle of incidence (i) = angle of reflection (r) • Dotted line is the normal. • Blue line is incident ray. • Red line is reflected ray. • Solid black line is a mirror. i r

49. Light and sound 3.16 construct ray diagrams to illustrate the formation of a virtual image in a plane mirror Object Image

50. Light and sound 3.17 describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms • The solid is glass. • The refracted ray bends towards the normal because glass is denser than air. • The emergent ray bends away from the normal because air is less dense than glass. • How much it bends depends on the refractive index.