RCSI Introduction to General Physics 1 PDF

Introduction to General Physics 1 M 6.1.1 Introduction to Physics Dr Orlaith Brennan  Learning Outcomes On completion of this lecture, students will be able to… Demonstrate an appreciation of what physics is* Be aware of why you are studying physics* Identify the import...

Introduction to General Physics 1 M 6.1.1 Introduction to Physics Dr Orlaith Brennan  Learning Outcomes On completion of this lecture, students will be able to… Demonstrate an appreciation of what physics is* Be aware of why you are studying physics* Identify the importance of measurement and the International System of Units Recall the basic quantities, their symbol(s) and the corresponding SI unit and symbol Employ base units to derive other units Convert between normal numbers and scientific notation Recall common biomedical prefixes Apply the basic rules of manipulating powers and scientific notation, i.e. add, subtract, multiply and divide Differentiate between vector and scalar quantities Recall the area and volume of basic shapes Recognise the Greek alphabet 2 * Will not be assessed  What is Physics? Physics is derived from the Greek word physis meaning nature. Physics is the ‘Mother’ of science. Physics is science at its fundamental. Without physics, our world as we know it today would not function. 3  What is Physics? It is the study of everything… asking fundamental questions and trying to answer them by observing and experimenting. Physics is the study of matter and energy and their interaction. Energy 4  What is Physics? ⚛ Mechanics and Motion ⚛ Thermodynamics ⚛ Gravity ⚛ Waves ⚛ Sound ⚛ Light and Optics ⚛ Electricity and Magnetism ⚛ Atomic Physics 5  Why Study Physics? Students of many fields study physics because of the role it plays in all phenomena. What areas of physics are important in healthcare professions? o Mechanics – describes how the body moves o Optics – determines how we can visualise objects o Fluid flow – explains blood flow o Electricity – basis of nerve and heart function o Nuclear Physics – origin of medical imaging, diagnostics and therapeutics Studying physics strengthens reasoning and problem- 6 solving skills that are valuable in areas far beyond physics.  Develop your Knowledge Know Why Know What Know How Know Nothing 7  Studying Physics It’s not all about complicated equations and maths! 8  Experiments in Physics Physics is an experimental science Measurements → Data Observation, reason, and experiment make up what we call the scientific method. Experiment Any property of matter that can be measured is called a physical quantity (a quantity). Measurement Examples of quantities? 9 Physical Quantity  Understanding Measurement How long is this line? Measuring: when you measure a quantity you compare it with a standard amount of the same quantity. The standard amount is called a unit. 10  We need a standard unit! The metre* The result of a measurement is always a number multiplied by a unit. The number and unit is called the magnitude. 3 metres 3 times the standard unit * Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level). For a long time it had been agreed internationally that the meter would be defined as the distance between two scratches on a bar kept in a laboratory in France. Since 1983, it has been defined as the length of the path 11 travelled by light in vacuum during a time interval of 1/299,792,458 of a second.  International System of Units (SI Units) In 1960 scientists agreed on a particular system of units. International System of Units (SI Units) (Le Système International d'unites) 12 * One second is 1/86,400 of an average day  Basic Units (Base Units) To simplify and help relate 7* different quantities, basic quantities, were chosen and corresponding basic units Basic Symbol Name of SI Symbol Quantity basic unit Length l or s metre m Time t second s Mass m kilogram kg Electric ampere A current Temperature T kelvin K 13 * We only look at 5  Derived Units Basic quantity – length (l) 1 metre (1 m) Derived quantity – area (A) Derived quantity – volume (V) Area = Length x Width Volume = Length x Width x Height = 1m x 1m = 1m x 1m x 1m = 1 square metre (1 m2) 1 cubed metre (1 m3) 14  Derived Units The unit of any quantity can be written as a product (multiplication) or quotient (division) of one or more base units. The unit of every other quantity is called a derived unit. 15  Derived Units - Problem Density is defined as Mass/Volume What is the SI unit of density? Mass = kg Volume = m3 → Density = kg/m3 or kg m-3 Remember, as long as you know the formula, you 16 can determine the units.  Why are units important? The units on both sides of an equation must be equal to ensure the equation is valid. Left hand side unit = Right hand side unit Remember this sign indicates that the two sides have the same value. Velocity (m/s) = Distance (m) / Time (s) Velocity (km/hr) ≠ Distance (m) / Time (s) 17  Using SI Units Ensure that the value of each quantity is expressed in the correct SI unit when solving problems, e.g. convert hour, day, etc. to seconds. E.g. Speed is measured in m/s therefore distance and time must be measured in metres and seconds, respectively. Ensure that when doing calculations your answer has the correct associated units. It is not sufficient to just put down a number. 18 Marks will be lost in exams if you fail to include units!  Derived Units The units of some physical quantities can be complicated. Therefore, they are replaced with a different name and symbol. 19  Powers Values of SI units can sometimes be loo large or too small to use – multiples or fractions are used. Powers, scientific notation, exponential notation and exponents - all essentially mean the same thing. The numbers that you’re multiplying together are called the “base”. We typically deal with base 10. The number of times you multiply them together is called the exponent. So, 10,000 which is 10 x 10 x 10 x 10 is written as “ten to the power of four” or 104, 20 10 is the base and 4 is the exponent.  Other Ways of Writing It We can use the ^ symbol, as it is easy to type. Example: 3 × 10^4 is the same as 3 × 104 3×10^4 = 3 × 10 × 10 × 10 × 10 = 30,000 Calculators often use E or e: Example: 6E+5 is the same as 6 × 105 6E+5 = 6 × 10 × 10 × 10 × 10 × 10 = 600,000 Example: 3.12e4 is the same as 3.12 × 104 21  Powers of 10 10x : x is positive so the number is >1 101 = just one ten = 10 102 = 2 tens multiplied together = 10 x 10 = 100 103 = 3 tens multiplied together = 10 x 10 x 10 = 1000 x tells us how many times to multiply by the base, in this case how many times we multiply 10 x also tells us how many times to move the decimal place 3.6 x 1012 → → → 3600,000,000,000 x also tells us how many digits are after the first number 100 = ? 22  Scientific Notation (Standard Form) Write 312,000,000,000 in scientific notation: 1. Move the decimal place to the left to create a new number from 1 up to 10. m = 3.12 2. Determine the exponent, which is the number of times you moved the decimal. In this example, you moved the decimal 11 times; also, because you moved the decimal to the left, the exponent is positive. Therefore, n = 11 3. Put the number in the correct form for scientific notation 23 3.12 x 1011  Powers of 10 10-x: x is negative, so the number is