CIE A Level Physics PDF

Head to www.savemyexams.com for more awesome resources CIE A Level Physics Your notes 1.1 Physical Quantities & Units Contents 1.1.1 Physical Quantities 1.1.2 SI Units 1.1.3 Homogeneity of Physical Equations...

Head to www.savemyexams.com for more awesome resources CIE A Level Physics Your notes 1.1 Physical Quantities & Units Contents 1.1.1 Physical Quantities 1.1.2 SI Units 1.1.3 Homogeneity of Physical Equations & Powers of Ten 1.1.4 Scalars & Vectors Page 1 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 1.1.1 Physical Quantities Your notes What is a Physical Quantity? Speed and velocity are examples of physical quantities; both can be measured All physical quantities consist of a numerical magnitude and a unit In physics, every letter of the alphabet (and most of the Greek alphabet) is used to represent these physical quantities These letters, without any context, are meaningless To represent a physical quantity, it must contain both a numerical value and the unit in which it was measured The letter v be used to represent the physical quantities of velocity, volume or voltage The units provide the context as to what v refers to If v represents velocity, the unit would be m s–1 If v represents volume, the unit would be m3 If v represents voltage, the unit would be V All physical quantities must have a numerical magnitude and a unit Page 2 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Estimating Physical Quantities There are important physical quantities to learn in physics Your notes It is useful to know these physical quantities, they are particularly useful when making estimates A few examples of useful quantities to memorise are given in the table below (this is by no means an exhaustive list) Estimating Physical Quantities Table Worked example Estimate the energy required for an adult man to walk up a flight of stairs. Page 3 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Exam Tip The mark scheme for calculations involving estimates are normally quite generous and offer a range of values as the final answer. Some common estimates are: Mass of an adult = 70 kg Gravitational field strength, g = 10 m s-2 Mass of a car = 1500 kg Wavelength of visible light = 400 nm (violet) – 700 nm (red) Many values are already given in your data booklet that therefore may not be given in the question, so make sure to check there too! Page 4 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 1.1.2 SI Units Your notes SI Base Quantities There is a seemingly endless number of units in Physics These can all be reduced to six base units from which every other unit can be derived These six units are referred to as the SI Base Units; this is the only system of measurement that is officially used in almost every country around the world SI Base Quantities Table Exam Tip You will only be required to use the first five SI base units in this course, so make sure you know them! Page 5 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Derived Units Derived units are derived from the seven SI Base units Your notes The base units of physical quantities such as: Newtons, N Joules, J Pascals, Pa, can be deduced To deduce the base units, it is necessary to use the definition of the quantity The Newton (N), the unit of force, is defined by the equation: Force = mass × acceleration N = kg × m s–2 = kg m s–2 Therefore, the Newton (N) in SI base units is kg m s–2 The Joule (J), the unit of energy, is defined by the equation: Energy = ½ × mass × velocity2 J = kg × (m s–1)2 = kg m2 s–2 Therefore, the Joule (J) in SI base units is kg m2 s–2 The Pascal (Pa), the unit of pressure, is defined by the equation: Pressure = force ÷ area Pa = N ÷ m2 = (kg m s–2) ÷ m2 = kg m–1 s–2 Therefore, the Pascal (Pa) in SI base units is kg m–1 s–2 Page 6 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 1.1.3 Homogeneity of Physical Equations & Powers of Ten Your notes Homogeneity of Physical Equations An important skill is to be able to check the homogeneity of physical equations using the SI base units The units on either side of the equation should be the same To check the homogeneity of physical equations: Check the units on both sides of an equation Determine if they are equal If they do not match, the equation will need to be adjusted How to check the homogeneity of physical equations Page 7 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Powers of Ten Physical quantities can span a huge range of values Your notes For example, the diameter of an atom is about 10–10 m (0.0000000001 m), whereas the width of a galaxy may be about 1021 m (1000000000000000000000 m) This is a difference of 31 powers of ten Powers of ten are numbers that can be achieved by multiplying 10 times itself It is useful to know the prefixes for certain powers of ten Powers of Ten Table Exam Tip You will often see very large or very small numbers categorised by powers of ten, so it is very important you become familiar with these as getting these prefixes wrong is a very common exam mistake! Page 8 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 1.1.4 Scalars & Vectors Your notes What are Scalar & Vector Quantities? A scalar is a quantity which only has a magnitude (size) A vector is a quantity which has both a magnitude and a direction For example, if a person goes on a hike in the woods to a location which is a couple of miles from their starting point As the crow flies, their displacement will only be a few miles but the distance they walked will be much longer Displacement is a vector while distance is a scalar quantity Distance is a scalar quantity because it describes how an object has travelled overall, but not the direction it has travelled in Displacement is a vector quantity because it describes how far an object is from where it started and in what direction There are a number of common scalar and vector quantities Scalars and Vectors Table Page 9 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Exam Tip Do you have trouble figuring out if a quantity is a vector or a scalar? Just think - can this quantity have a minus sign? For example - can you have negative energy? No. Can you have negative displacement? Yes! Page 10 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Combining Vectors Vectors are represented by an arrow Your notes The arrowhead indicates the direction of the vector The length of the arrow represents the magnitude Vectors can be combined by adding or subtracting them from each other There are two methods that can be used to combine vectors: the triangle method and the parallelogram method To combine vectors using the triangle method: Step 1: link the vectors head-to-tail Step 2: the resultant vector is formed by connecting the tail of the first vector to the head of the second vector To combine vectors using the parallelogram method: Step 1: link the vectors tail-to-tail Step 2: complete the resulting parallelogram Step 3: the resultant vector is the diagonal of the parallelogram When two or more vectors are added together (or one is subtracted from the other), a single vector is formed and is known as the resultant vector Vector Addition Page 11 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Page 12 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Vector Subtraction Page 13 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Page 14 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Condition for Equilibrium Coplanar forces can be represented by vector triangles In equilibrium, these are closed vector triangles. The vectors, when joined together, form a closed path If three forces acting on an object are in equilibrium; they form a closed triangle Page 15 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Resolving Vectors Two vectors can be represented by a single resultant vector that has the same effect Your notes A single resultant vector can be resolved and represented by two vectors, which in combination have the same effect as the original one When a single resultant vector is broken down into its parts, those parts are called components For example, a force vector of magnitude F and an angle of θ to the horizontal is shown below It is possible to resolve this vector into its horizontal and vertical components using trigonometry Page 16 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources For the horizontal component, Fx = Fcosθ For the vertical component, Fy = Fsinθ Your notes Page 17 of 17 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers