Physics A FNSC 1044 Lecture Notes PDF - City University Malaysia

PHYSICS A FNSC 1044 Prepared by : AMMER EZHAR BIN MOHD RAZALLI [email protected] CITY UNIVERSITY MALAYSIA 4th Jan 2022 Learning Outcomes AT THE END OF THIS UNDERSTAND THE UNDERSTAND THE SCALAR UNDERSTANDING THE CHAPTER STUDENT PHYSICAL UNITS AND AND V...

PHYSICS A FNSC 1044 Prepared by : AMMER EZHAR BIN MOHD RAZALLI [email protected] CITY UNIVERSITY MALAYSIA 4th Jan 2022 Learning Outcomes AT THE END OF THIS UNDERSTAND THE UNDERSTAND THE SCALAR UNDERSTANDING THE CHAPTER STUDENT PHYSICAL UNITS AND AND VECTOR QUANTITIES MEASUREMENT SHOULD BE ABLE TO: DERIVED QUANTITIES TECHNIQUES WHAT IS PHYSICS?? -The word “Physics” come from Greek word “Physikos” which means knowledge of nature -The goal of physics is to gain a better understanding of the world and to explain the fundamental nature of the universe -Generally, the questions “why?’’ and “how?” help us to find answers that are related to the mysteries of the universe. -This majority of the natural phenomena can be explained by using the principle of physics  Classical Physics (Motion, Light, Electricity, Magnetism, Heat, Mechanics, Fluids, Sound) Fields of studies in physics Modern Physics (Atomic, Molecular, Electron physics, Nuclear physics, Particle physics, Relativity, Quantum Theory, Structure) Important of physics Physics is important in science such as astronomy, biology, chemistry and geology Used in practical developments in engineering, medicine and othertechnology Research in physics led us to the studies of radioactive materials, diagnosis and treatment of certain diseases. Contribution of physics to mankind YEAR DISCOVERY AND CONTRIBUTION BASED ON PHYSICS 1896-98 Discovery of radioactivity 1897 Discovery of the electron 1900 Discovery of quantum energy Electromagnetic waves across the Atlantic Ocean (Transatlantic telegraph 1901 cables) 1905 The Theory of Relativity Physical Quantities and Units 1.1 Physical Quantities 1.2 SI Units 1.3 Homogeneity of Physical Equations 1.4 Scalars & Vectors 1.5 Measurements & Error  1.1 Physical Quantities 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  Estimating Physical Quantities There are important physical quantities to learn in physics 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) 1.2 SI Units 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 seven 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 Derived Units Derived units are derived from the seven SI Base units 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 1.3 Homogeneity of Physical Equations Strain (Deformation) An important skill is to be able to check the homogeneity of physical equations using the SI Strain is defined as "deformation of a solid due base units to stress". The units on either side of the equation should be the same Normal strain - elongation or contraction of a To check the homogeneity of physical equations: line segment Check the units on both sides of an equation Shear strain - change in angle between two line Determine if they are equal segments originally perpendicular If they do not match, the equation will need to be Normal strain and can be expressed as adjusted ε = dl / lo =σ/E dl = change of length (m, in) lo = initial length (m, in) ε = strain - unit-less Prefixes/Powers of Ten Example The thickness of a film is 25nm. What is the thickness in unit meter? Answer nano (n) = 0.000000001 or 10-9 Therefore 25nm = 25 x 10-9 m Example 0.255 s is equal to how many ms. Answer milli (m) = 0.001 or 10-3 To write a normal number with prefixes, we divide the number with the value of the prefixes 0.255 s = 0.255 ÷ 10-3 = 255 ms  1.4 Scalars & Vectors 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 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 Combining Vectors Vectors are represented by an arrow 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 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 Resolving Vectors Two vectors can be represented by a single resultant vector that has the same effect 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 For the horizontal component, Fx = Fcosθ For the vertical component, Fy = Fsinθ 1.5 Measurements & Error Measurement technique Common instruments used in Physics are: Metre ruler – to measure distance and length Balances – to measure mass Protractors – to measure angles Stopwatches – to measure time Ammeters – to measure current Voltmeters – to measure potential difference More complicated instruments such as the micrometer screw gauge and Vernier calipers can be used to more accurately measure length  Measurements of quantities are made with the aim of finding the true Error value of that quantity In reality, it is impossible to obtain the true value of any quantity, there will always be a degree of uncertainty The uncertainty is an estimate of the difference between a measurement reading and the true value Random and systematic errors are two types of measurement errors which lead to uncertainty Random Error Systematic Error Random errors cause unpredictable Systematic errors arise from the use of fluctuations in an instrument’s readings faulty instruments used or from flaws in as a result of uncontrollable factors, such the experimental method as environmental conditions This type of error is repeated every time Zero Error This affects the precision of the the instrument is used or the method is measurements taken, causing a wider This is a type of systematic error followed, which affects the accuracy of all which occurs when an instrument spread of results about the mean value readings obtained gives a reading when the true reading is zero To reduce systematic errors: instruments To reduce random error: repeat should be recalibrated or the technique This introduces a fixed error into measurements several times and readings which must be accounted being used should be corrected or calculate an average from them for when the results are recorded adjusted Precision and Accuracy Precision of a measurement: this is how close the measured values are to each other; if a measurement is repeated several times, then they can be described as precise when the values are very similar to, or the same as, each other The precision of a measurement is reflected in the values recorded – measurements to a greater number of decimal places are said to be more precise than those to a whole number Accuracy: this is how close a measured value is to the true value; the accuracy can be increased by repeating measurements and finding a mean average Uncertainty There is always a degree of uncertainty when measurements are taken; the uncertainty can be thought of as the difference between the actual reading taken (caused by the equipment or techniques used) and the true value Uncertainties are not the same as errors Errors can be thought of as issues with equipment or methodology that cause a reading to be different from the true value The uncertainty is a range of values around a measurement within which the true value is expected to lie, and is an estimate For example, if the true value of the mass of a box is 950 g, but a systematic error with a balance gives an actual reading of 952 g, the uncertainty is ±2 g These uncertainties can be represented in a number of ways: Absolute Uncertainty: where uncertainty is given as a fixed quantity Fractional Uncertainty: where uncertainty is given as a fraction of the measurement Percentage Uncertainty: where uncertainty is given as a percentage of the measurement Thank You The study of physics is also an adventure. You will find it challenging, sometimes frustrating, occasionally painful, and often richly rewarding.” - Hugh D. Young