2. Socrative Room A8NJ7P8V

3. Noadswood Science, 2012 A8NJ7P8V

4.  Speed and velocity represent how fast you are going (measured in m/s or mph or km/h etc…)  However, there is a subtle difference between the two: -  Speed = how fast you are going (e.g. 100mph)  Velocity = how fast you are going (e.g. 100mph) with a direction (e.g. North)  Two moving objects can have the same speed, but completely different velocities – e.g. a car travelling North at 50mph and a car travelling South at 50mph have the same speed, but their velocities are not the same as they are moving in opposite directions A8NJ7P8V

5.  What is acceleration?  Acceleration is a measurement of how quickly the velocity is changing (i.e. how quickly you’re speeding up or slowing down (when decelerating)) A8NJ7P8V

6.  Acceleration is the change in velocity (ΔV) ÷ time (t) Acceleration (a) Change In Velocity (ΔV) Time (t) Acceleration = Change In Velocity  Time Time = Change In Velocity  Acceleration Change In Velocity = Acceleration x Time A8NJ7P8V

7.  To work out acceleration you must first find the change in velocity (v-u (where v is the final velocity and u the initial velocity))  Then ÷ by the time  Finally acceleration has a unit of m/s 2 (unlike velocity = m/s) a ΔV t  E.g. a cat accelerates from a walking pace of 2m/s to 6m/s in 5.6 seconds – what is acceleration? Change of velocity = 6 – 2 = 4 4 ÷ 5.6 = 0.71m/s 2 A8NJ7P8V

8.  Two car rivals claim their cars are the fastest accelerating – these are tested on a straight track with velocity recorders fitted  The results are shown below – graph the acceleration of the two cars from standstill to their top speed, and identify which accelerated fastest Time from standing start (seconds) 024681012 Velocity of car A (m/s) 0816243240 Velocity of car B (m/s) 0102030 A8NJ7P8V

9. What is the acceleration of each car? A8NJ7P8V

10.  Car A top speed = 40m/s reached in 10 seconds  Car B top speed = 30m/s reached in 6 seconds Acceleration = change in velocity (m/s) ÷ time (s)  Car A acceleration: - Change in velocity = 40m/s – 0m/s = 40m/s Time taken = 10s Acceleration = 40m/s ÷ 10s = 4m/s 2 A8NJ7P8V

11.  Car A top speed = 40m/s reached in 10 seconds  Car B top speed = 30m/s reached in 6 seconds Acceleration = change in velocity (m/s) ÷ time (s)  Car B acceleration: - Change in velocity = 30m/s – 0m/s = 30m/s Time taken = 6s Acceleration = 30m/s ÷ 6s = 5m/s 2 A8NJ7P8V

12.  In terms of performance 60mph is ~27m/s  Car B reaches 60 in just over 5 seconds, whilst it takes car A almost 7 seconds  However, car A’s lesser acceleration is weighed against its higher top speed of 89mph (40m/s) against the 67mph (30m/s) of car B A8NJ7P8V

13.  What is deceleration?  Deceleration (negative acceleration) is where an object slows down (such as when a driver applies the breaks) A8NJ7P8V

14. 1. Complete a) to c) using the key words: acceleration; speed; and velocity a) An object moving steadily round in a circle has a constant… b) If the velocity of an object increases by the same amount every second, its … is constant c) Deceleration is when the … of an object decreases 2. The velocity of a car increased from 8m/s to 28m/s in 8s without changing its direction. Calculate its change in velocity and its acceleration 3. A man moving at 2m/s accelerates by 3m/s 2 for 2.5s. Calculate his new velocity A8NJ7P8V

15. 1. a) An object moving steadily round in a circle has a constant speed b) If the velocity of an object increases by the same amount every second, its acceleration is constant c) Deceleration is when the velocity of an object decreases 2. Change in velocity = 28m/s – 8m/s = 20m/s Acceleration 20m/s ÷ 8s = 2.5m/s 2 3. Acceleration = 3m/s 2 Time = 2.5s Velocity = 7.5m/s 7.5m/s + 2m/s (original velocity) = 9.5m/s 2 A8NJ7P8V

16. Velocity-Time Graphs  Remember, the velocity of an object is its speed in a particular direction (this means that two cars travelling at the same speed, but in opposite directions, have different velocities)  When an object is moving with a constant velocity, the line on the graph is horizontal  When an object is moving with a constant acceleration, the line on the graph is straight, but sloped  The steeper the line, the greater the acceleration of the object A8NJ7P8V

17. Acceleration  Acceleration is represented on a velocity-time graph by the gradient of the line (change in velocity ÷ time)  What is the acceleration - represented by the sloping line?  To find the distance we need to calculate the area of the light blue and dark blue regions  For rectangular areas use the formula base x height = 6s x 8m/s = 48m  For triangular areas use the formula ½ x base x height = ½ x 4s x 8m/s = 16m Distance = 48 + 16 = 64m A8NJ7P8V

18. Distance  The area under the line on a velocity-time graph represents the distance travelled  What distance was covered on the above graph?  Change in velocity from 0m/s to 8m/s = 8m/s  Time of 4 seconds for change in velocity 8 ÷ 4 = 2m/s 2 A8NJ7P8V

19. Past paper question A8NJ7P8V

20. Past paper question A8NJ7P8V

21. Past paper question A8NJ7P8V

22. Practice Question 1  Match A, B, C and D to the following descriptions: - 1. Accelerated motion throughout 2. Zero acceleration 3. Accelerated motion, then decelerated motion 4. Deceleration  Which line represents the furthest distance?  Which line represents the least distance? A8NJ7P8V

23. Practice Question 1 – Answer  Match A, B, C and D to the following descriptions: - 1. Accelerated motion throughout – A ( 1/2 x 20s x 8m/s = 80m) 2. Zero acceleration – C (20s x 8m/s = 160m) 3. Accelerated motion, then decelerated motion – D ( 1/2 x 20s x 6m/s = 60m) 4. Deceleration – B ( 1/2 x 20s x 4m/s = 40m)  Which line represents the furthest distance? – C  Which line represents the least distance? – B A8NJ7P8V

24. Practice Question 2  Describe the motion of the cyclist  Work out the initial acceleration  Work out the distance travelled by the cyclist in the first 40 seconds A8NJ7P8V

25. Practice Question 2 – Answer  Describe the motion of the cyclist – accelerates at constant rate for 40 seconds, then decelerates for the next 20 seconds to a standstill  Work out the initial acceleration – 0.2m/s 2 (8m/s ÷ 40s)  Work out the distance travelled by the cyclist in the first 40 seconds – ½ x 40s x 8m/s = 160m A8NJ7P8V

26. Practice Question 3  Plot a velocity-time graph of these results What was the initial acceleration? How far did it travel in the first 20 seconds? How far did it travel in the next 10 seconds?  In a motorcycle test the speed from rest was recorded at intervals Time (s)051015202530 Velocity (m/s)010203040 A8NJ7P8V

27. Practice Question 3 – Answer  What was the initial acceleration – 2m/s 2 (40m/s ÷ 20s)  How far did it travel in the first 20 seconds – ½ x 20s x 40m/s = 400m  How far did it travel in the next 10 seconds – 40 x 10 = 400m A8NJ7P8V

28. Electricity

29. Basic ideas… Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____. Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______. Resistance is anything that resists an electric current. It is measured in _____.” (Words: volts, amps, ohms, voltage, ammeter, voltmeter) A8NJ7P8V

30. More basic ideas… If a battery is added the current will ________ because there is a greater _____ on the electrons If a bulb is added the current will _______ because there is greater ________ in the circuit A8NJ7P8V

31. Current in a series circuit If the current here is 2 amps… The current here will be… And the current here will be… In other words, the current in a series circuit is THE SAME at any point A8NJ7P8V

32. Current in a parallel circuit A PARALLEL circuit is one where the current has a “choice of routes” Here comes the current… And the rest will go down here… Half of the current will go down here (assuming the bulbs are the same)… A8NJ7P8V

33. Current in a parallel circuit If the current here is 6 amps The current here will be… And the current here will be… A8NJ7P8V

34. Voltage in a series circuit V VV If the voltage across the battery is 6V… …and these bulbs are all identical… …what will the voltage across each bulb be? 2V A8NJ7P8V

35. Voltage in a series circuit V V If the voltage across the battery is 6V… …what will the voltage across two bulbs be? 4V A8NJ7P8V

36. Voltage in a parallel circuit If the voltage across the batteries is 4V… What is the voltage here? And here? VV 4V A8NJ7P8V

37. Past Paper Question A8NJ7P8V

38. Past Paper Question A8NJ7P8V

39. Past Paper Question A8NJ7P8V

40. Summary In a SERIES circuit: Current is THE SAME at any point Voltage SPLITS UP over each component In a PARALLEL circuit: Current SPLITS UP down each “strand” Voltage is THE SAME across each”strand” A8NJ7P8V

41. An example question: V1V1 V2V2 6V 3A A1A1 A2A2 V3V3 A3A3 A8NJ7P8V

42. Advantages of parallel circuits… There are two main reasons why parallel circuits are used more commonly than series circuits: 1)Extra appliances (like bulbs) can be added without affecting the output of the others 2)If one appliance breaks it won’t affect the others either A8NJ7P8V

43. Georg Simon Ohm 1789-1854Resistance Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. The resistance of a component can be calculated using Ohm’s Law: Resistance = Voltage (in V) (in  )Current (in A) V RI A8NJ7P8V

44. An example question: V A 1)What is the resistance across this bulb? 2)Assuming all the bulbs are the same what is the total resistance in this circuit? Voltmeter reads 10V Ammeter reads 2A A8NJ7P8V

45. Current-voltage graphs I V I V I V 1. Resistor 3. Diode 2. Bulb Explain the shape of each graph A8NJ7P8V

46. Three simple components: 1)Diode – only lets current flow in one direction 2)Light dependant resistor – resistance DECREASES when light intensity INCREASES 3)Thermistor – resistance DECREASES when temperature INCREASES A8NJ7P8V

47. Wiring a plug A8NJ7P8V

48. DC and AC DC stands for “Direct Current” – the current only flows in one direction: AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz) 1/50 th s 240V V V Time T A8NJ7P8V

49. Fuses Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____. Words – large, harm, safety, melt, live, circuit, fuse A8NJ7P8V

50. Circuit breakers If the current becomes too high the __________ is activated. This will ______ the iron and the contact will be _______. This will break the circuit. Circuit breakers have two main advantages over fuses: they work ______ and can easily be ______. Words – electromagnet, broken, attract, reset, quicker A8NJ7P8V

51. Earth wires Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows. Words – fuse, fault, metal, surges, touch A8NJ7P8V

52. Power and fuses Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by: P IV Power = voltage x current in W in V in A Using this equation we can work out the fuse rating for any appliance. For example, a 3kW (3000W) fire plugged into a 240V supply would need a current of _______ A, so a _______ amp fuse would be used (fuse values are usually 3, 5 or 13A). A8NJ7P8V

53. Power and fuses Copy and complete the following table: AppliancePower rating (W) Voltage (V)Current needed (A) Fuse needed (3, 5 or 13A) Toaster720240 Fire2000240 Hairdryer300240 Hoover1000240 Computer100240 Stereo80240 A8NJ7P8V

54. Charge (Q) As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation: Q TI Charge = current x time (in C) (in A) (in s) A8NJ7P8V

55. Example questions Charge (C)Current (A)Time (s) 52 0.41 200.5 50250 360 1)A circuit is switched on for 30s with a current of 3A. How much charge flowed? 2)During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for? 3)A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed? A8NJ7P8V

56. Energy and charge The amount of energy that flows in a circuit will depend on the amount of charge carried by the electrons and the voltage pushing the charge around: E QV Energy transferred = charge x voltage (in J) (in C) (in V) A8NJ7P8V

57. Example questions 1)In a radio circuit a voltage of 6V is applied and a charge of 100C flows. How much energy has been transferred? 2)In this circuit the radio drew a current of 0.5A. How long was it on for? 3)A motor operates at 6V and draws a current of 3A. The motor is used for 5 minutes. Calculate: a) The motor’s resistance, b) the charge flowing through it, c) the energy supplied to it 4)A lamp is attached to a 12V circuit and a charge of 1200C flows through it. If the lamp is on for 10 minutes calculate a) the current, b) the resistance, c) the energy supplied to the bulb. A8NJ7P8V

58. GCSE Radiation A8NJ7P8V

59. Structure of the atom A hundred years ago people thought that the atom looked like a “plum pudding” – a sphere of positive charge with negatively charged electrons spread through it… I did an experiment that proved this idea was wrong. I called it the “Rutherford Scattering Experiment” Ernest Rutherford, British scientist: A8NJ7P8V

60. The Rutherford Scattering Experiment Alpha particles (positive charge) Thin gold foil Some particles passed through, some were deflected backwards Conclusion – atom is made up of a small central nucleus surrounded by electrons orbiting in shells A8NJ7P8V

61. The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”) A8NJ7P8V

62. The structure of the atom ParticleRelative MassRelative Charge Proton11 Neutron10 Electron0 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously) A8NJ7P8V

63. Background Radiation Radon gas Food Cosmic rays Gamma rays Medical Nuclear power 13% are man-made A8NJ7P8V

64. Isotopes An isotope is an atom with a different number of neutrons: Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more. Notice that the mass number is different. How many neutrons does each isotope have? A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating. A8NJ7P8V

65. Types of radiation 1) Alpha (  ) – an atom decays into a new atom and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom) 2) Beta (  ) – an atom decays into a new atom by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle. 3) Gamma – after  or  decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The atom is not changed. Unstable nucleus New nucleus Alpha particle Beta particle Gamma radiation A8NJ7P8V

66. Radioactivity If a substance is capable of ALWAYS emitting radiation under any conditions we say it is ____________. There are three types of radiation: ALPHA, _____ and GAMMA. These types of radiation are always given off by rocks, _____, building materials, air and cosmic rays around us – this is called BACKGROUND RADIATION. Each type is capable of penetrating different materials:    Sheet of paper Few mm of _________ Few cm of lead Words – aluminium, beta, food, radioactive A8NJ7P8V

67. Industrial Uses of radioactivity 1) Medical uses – gamma rays can be used to destroy cancerous cells or to sterilise medical instruments Gamma Source All the equipment is already vacuum sealed inside the box. The gamma waves kill all bacteria as they pass through. The equipment is sterile until opened in the operating theatre. A8NJ7P8V

68. Uses of radioactivity 2) Tracers – a tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe: Gamma source Tracers can also be used to develop better plant fertilisers. The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected. A8NJ7P8V

69. Rollers Beta emitter Beta detector Paper Industrial Uses of radioactivity : Beta Automatic Thickness control. A8NJ7P8V

70. Industrial Uses of radioactivity : Alpha SMOKE ALARM A8NJ7P8V

71. Past Paper Question A8NJ7P8V

72. Past Paper Question A8NJ7P8V

73. Nuclear fission Uranium nucleus Unstable nucleus New nuclei (e.g. barium and krypton) More neutrons Neutron A8NJ7P8V

74. Chain reactions Each fission reaction releases neutrons that are used in further reactions. A8NJ7P8V

75. Fission reactions summary Each fission reaction releases energy in the form of _______. In a nuclear power plant this heat is used to boil _______, which is used to drive turbines etc. The energy from each reaction is very ______, but there are ________ of reactions every second. The waste products from these reactions are __________, which is why nuclear power plants are ___________. Words – radioactive, water, billions, controversial, heat, small A8NJ7P8V

76. Half Life Lesson Lesson objectives To know what is meant by the term “ Half Life” To understand that levels of radioactivity can be predicted using the half life of radioactive substances. To be able to use this knowledge to calculate the age of natural objects such as rocks from their level of radioactivity. A8NJ7P8V

77. Half Life Lesson Introduction… Predicting the future. A8NJ7P8V

78. Answer: At least 7 Half Life Lesson Question: How many people are born between the 1 st and 10 th of the month. A8NJ7P8V

79. Half Life Lesson What does the word random mean? Oxford dictionary says.. Having no specific pattern, purpose, or objective A8NJ7P8V

80. Half Life Lesson Which dot do you think will change colour? Its random dears A8NJ7P8V

81. Half life The decay of radioisotopes can be used to measure the material’s age. The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay… At start there are 16 radioisotopes After 1 half life half have decayed (that’s 8) After 3 half lives another 2 have decayed (14 altogether) After 2 half lives another half have decayed (12 altogether) = radioisotope= new atom formed A8NJ7P8V

82. Number of popcorn remaining 16 12 8 4 0 0 10 20 30 40 50 Time (s) HALF LIFE OF POPCORN = 10s Example of half life using pan of popcorn ‘popping’ A8NJ7P8V

83. A radioactive decay graph Time Count 1 half life2nd You cannot predict when a nucleus will decay, but you can predict the half life. 3rd A8NJ7P8V

84. Plenary As always you can tweet the lesson on www.rhymney.tk www.rhymney.tk Use the BBC Bitesize Activity to test what you have learnt today..(go to stage 4.)BBC Bitesize Activity Half Life Lesson A8NJ7P8V

85. Ionisation When radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.  particle Electron A8NJ7P8V

86. Dangers of radioactivity OUTSIDE the body  and  are more dangerous as  radiation is blocked by the skin. INSIDE the body an  source causes the most damage because it is the most ionising. Alpha Beta Gamma Radiation will ionise atoms in living cells – this can damage them and cause cancer or leukaemia. A8NJ7P8V

87. Dating materials using half-lives Question: Uranium decays into lead. The half life of uranium is 4,000,000,000 years. A sample of radioactive rock contains 7 times as much lead as it does uranium. Calculate the age of the sample. 8 8 Answer: The sample was originally completely uranium… …of the sample was uranium 4 8 2 8 1 8 Now only 4/8 of the uranium remains – the other 4/8 is lead Now only 2/8 of uranium remains – the other 6/8 is lead Now only 1/8 of uranium remains – the other 7/8 is lead So it must have taken 3 half lives for the sample to decay until only 1/8 remained (which means that there is 7 times as much lead). Each half life is 4,000,000,000 years so the sample is 12,000,000,000 years old. 1 half life later… A8NJ7P8V

88. An exam question… (AQA 2001 Higher Paper) Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock? (3 marks) The rock must be 2 half lives old – 2.6 billion years A8NJ7P8V

89. Past papers KE and PE A8NJ7P8V

90. Past papers KE and PE A8NJ7P8V

91. Past papers KE and PE A8NJ7P8V