GCE 2008 with Edexcel AL Physics consists of 6 Units • Unit 1: Physics on the go • Unit 2: Physics at work • Unit 3: Exploring physics • Unit 4: Physics on the move • Unit 5: Physics from creation to collapse • Unit 6: Experimental physics The ‘theory’ units Unit 1: Physics on the go Unit 4: Physics on the move Unit 2: Physics at work Unit 5: Physics from creation to collapse • Assessed by written paper • Assessed by written paper • 1 hour 30 minutes • 1 hour 30 minutes • 80 marks • 80 marks • multiple choice questions, • multiple choice questions, short questions and long fewer short questions and questions more long questions • 40% of the AS marks • 40% of the A2 marks • 20% of the A level marks • 20% of the A level marks Multiple choice questions Advice: • Wider specification coverage than before • Only worth 10 marks from 80 • Do not spend too much time • Do these at the end? • Do not leave any blank Appendix 12 – page 179 General and mathematical requirements • Physical quantities and their units • Significant figures • Order of magnitude • Rate of change • Vectors and scalars • Graphs • Arithmetic and computation • Algebra • Geometry and trigonometry Physical quantities and their units • Understand the distinction between base and derived physical quantities and their S.I. Units. The base physical quantities: mass, length, time, electric current, temperature, amount of substance The base units: kilogram, metre, second, ampere, kelvin, mole Examples of questions Unit 1, Q3 Which of these units is the same as the newton? A kg m s–1 B kg m s–2 C kg m2 s–2 D kg m2 s–3 Examples of questions Unit 2, Q 13(a) What is the coulomb in base units? Charge = current x time So a coulomb is an Amp second or A s Examples of questions Unit 2, Q 15(b) The current I in a length of aluminium of cross sectional area A is given by the formula I = nev A Where is the charge on an electron. Show that the units on the left hand side of the equation are consistent with those on the right hand side. A = m–3 A s m s–1 m2 A = m–3 m m2 s s–1 A=A Here are three physical quantities. Work out the base unit for each quantity. • The Plank constant = 6.63 x 10-34 J s • kg m2 s-1 • Permittivity of space = 8.85 x 10-12 C V-1 m-1 • A2 kg-1 m-3 s4 • Coulomb law constant = 8.99 x 109 N m2 C-2 • kg m3 A-2 s-4 Units • Every value that is calculated must have a unit or the mark will be lost. • In ‘show that’ questions the unit will be given. • ‘Show that’ questions are used so that if students cannot do an early part of a questions they can use the given value to do later parts of the question. • In a ‘show that’ question students need to give one more significant figure than the value given. Examples of questions Unit 1, Q 11(a) The Saturn V rocket used in NASA’s space programme had a mass of 3.04 × 106 kg. It took off vertically with a thrust force of 3.40 × 107N. (a) Show that the resultant force on the rocket is about 4 × 106 N. resultant force = upward force – weight resultant force = upward force – mg resultant force = 3.40 × 107– 3.04 × 106 x 9.81 resultant force = 4.2 × 106 N Orders of magnitude • Appreciate the order of magnitude of common physical quantities. mass of a man? 70 kg height of a man? 1.8 m mass of a car? 1000 kg volume of the room? ????? speed of a sprinter? 10 m/s characters on the page of a book? (60 characters per line, 40 lines per page, 2 400 characters per page [6754 Jan ‘09]) Orders of magnitude • Make order of magnitude calculations. Check that the answer to a calculation makes sense. Beware of impossible answers e.g. photoelectrons moving faster than the speed of light. Graphs • plotting graphs • ‘line of best fit’ • y = mx + c • Gradient • area under a graph Familiarity with graphs • Direct proportionality y = kx must go through (0,0) • Inverse proportionality y = k/x check values of xy • Inverse square laws y = k/X2 check values of x2 y Examples of questions Unit 1 Q9 Velocity can be found from the A area under a displacement-time graph B area under a force-time graph C gradient of a displacement-time graph D gradient of an acceleration-time graph Examples of questions Unit 1 Q19 This question requires students to: • recognise proportionality from a straight line graph • find the gradient of the graph • calculate the area under the graph. Examples of questions Unit 2 Q22 This question requires students to: • plot points on a graph • draw a line (curve) of best fit • sketch a graph, given the axes. Examples of questions PHY5 June 09 This question required students to show inverse square relationship find an area under a graph Unit 3: Exploring physics • For international centres this will be assessed by written paper. • This paper aims to test knowledge of practical techniques without having to do a practical assessment. Unit 3: Exploring physics The international alternative to internal assessment: • 1 hour 20 minutes • 40 marks • Multiple choice questions, short questions and long questions • 20% of the total AS marks • 10% of the total A level marks Practicals • Suggested practicals for students to carry out are given in the specification. • Students may be asked to describe an experiment in Unit 1 or Unit 2 as well as unit 3. • Any appropriate method will gain marks. Students should be able to: • draw labelled diagrams of apparatus • draw circuit diagrams • state what measurements you would take • describe how to obtain accurate results • describe safety precautions • identify possible sources of error • calculate absolute and percentage errors • criticise sets of measurements • plan experiments • plot graphs • do calculations • calculate the mean of a set of data Examples of questions Unit 1 Q15 You are asked to determine the acceleration of free fall at the surface of the Earth, g, using a free fall method in the laboratory. Describe the apparatus you would use, the measurements you would take and explain how you would use them to determine g. Give one precaution you would take to ensure the accuracy of your measurements. • Ball bearing held by electromagnet • Break circuit to start timer. • Ball falls to break circuit to stop timer. • Labelled diagram of apparatus. • Time, t, recorded on electronic timer. • Distance fallen, s, measured on metre rule. • Repeat for 6 different values of s. • s = ut + ½ at2 • s = ½ gt2 • Plot graph of s (y axis) against t2 (x axis) • Gradient = ½ g • g = 2 x gradient Examples of questions Unit 1 Q19 (d) The student uses a camera to video the movement of the toy in front of a metre rule. The video is then used to find the maximum height reached by the toy. (i) Explain the advantage of using the video camera over making observations just by eye. (ii) The student repeats this procedure several times and records the following data: 0.45 m, 0.44 m, 0.36 m, 0.46 m, 0.45 m. mean maximum height = 0.45 m Why is the student justified in using 0.45 m as the mean?