Introduction To Fundamental Physics PDF

Introduction and Fundamental Physics Dr Irene Polycarpou Example of questions that we are trying to answer in the field of physics Physics is also called "the fundamental science" because all branches of natural science like chemistry and biology are constrained by laws of physics. ...

Introduction and Fundamental Physics Dr Irene Polycarpou Example of questions that we are trying to answer in the field of physics Physics is also called "the fundamental science" because all branches of natural science like chemistry and biology are constrained by laws of physics.  Physics in Medicine ✓ Basic knowledge of physical principles encountered in medicine background of physiological processes and as working principles of biomedical devices. ✓ Assess the risks connected with operation of diagnostic or therapeutic systems necessary to understand interaction of many physical agents with human body. ✓ Find new ways to advance medicine using the concepts and laws of physics Fundamentals of Physics Physicsts make observations and ask basic questions: How big is an object? How much mass does it have? How far did it travel? How do we answer these questions? We take measurements and express them in standard units. Why are standard units important? Why are standard units important?  Why are standard units important? I. To measure the quantities accurately. II. To convey the measurements to other people so that they understand those measurements accurately and follow the same further.  Why are standard units important? ANECDOTE  Why are standard units important? ANECDOTE September of 1999. NASA’s Mars Climate Orbiter has spent 10 months on Mars. And then it burned and broke into pieces.  Why are standard units important? ANECDOTE Problem: software controlling the orbiter’s thrusters. The software calculated the force that the thrusters needed to exert in pounds of force. A second piece of code that read this data assumed it was in the metric unit—“newtons per square meter”.  Why are standard units important? ANECDOTE How did it happen? 1. The propulsion engineers at Lockheed Martin in Colorado expressed force in pounds. But, it was standard practice to convert to metric units for space missions. 2. Engineers at NASA’s Jet Propulsion Lab assumed the conversion had been made. Spacecraft ended up dangerously close to the planet’s atmosphere where it presumably burned and broke into pieces. Fundamentals of Physics Physical quantity Something that can be measured. Unit must be stated to give an understanding of the scale of the measurement Measured quantity always compared to an established standard. has PERMANENCE and REPRODUCIBILITY  Standard Units Laws of physics expressed in terms of physical quantities. Physical quantity – something that can be measured. Every measurement or quantitative statement requires a unit. Scientists have agreed to use SI Units. It defines basic units for basic quantities of importance in nature. International System of Units (SI)  Derived and Secondary Units Are derived from standard units.  Not all countries use the International Standard of measurement (SI). USA is one of the few countries that uses the Imperial system. Pounds lb  Prefixes Useful in expressing physical quantities that are very large or very small. Example: Estimate the area of Singapore as 716.1 km2 instead of 716100000 m2. Physics explains things that are very, very large. Physics explains things that are very, very small.  29 Prefixes In medicine we study objects that span a wide range of sizes. The basic unit of length in the metric system is the meter (m). e.g. 1 meter is about the height of a 3year old child. For objects much larger or smaller than a meter, we add a prefix: Rules for scientific notation Rules for Scientific Notation Rules for Scientific Notation  36 Order of magnitude Video : https://www.youtube.com/watch?v=0fKBhvDjuy0  37 Order of magnitude Many small structures of our body are of size: 1mm - 1μm  38 Distances and Sizes Many small structures of our body are of size: 1mm - 1μm Human lungs: consist of a branching network of tubes through which air flows. These tubes end in small, nearly spherical air sacs called alveoli. Each alveolus has a diameter of about 200 μm with an increase diameter during inhalation. Conversion of Units Exercise 1: Convert the speed of 55 mi/h into meter per seconds. Exercise 2: The recommended tire pressure in a Honda Civic is 28 psi (pounds per square inch). What is the pressure in atmospheres (atm) ? Exercise 2: The recommended tire pressure in a Honda Civic is 28 psi (pounds per square inch). What is the pressure in atmospheres (atm) ? 1 Pa = 1 N/m2  Vectors and Scalars Examples Vector - quantity with magnitude (size) and direction. Vectors: Scalars: Displacement Distance Scalar - quantity with magnitude only. Velocity Speed Acceleration Time Momentum Mass Negative & Positive Vectors Force Energy Negative vector is a vector which will always be in the direction opposite the reference position direction. Vectors are represented with arrows The length of the arrow represents the magnitude (how far, how fast, how strong, etc, depending on the type of vector). But where do we put these vectors?  Coordinate Systems To determine the position of a moving or static object in the space, we need to know the coordinates. Rectangular or cartesian coordinates xy – coordinates which intercept perpendicularly at (0,0), origin point. Define any position of any point in the xy plane we write (x,y). Polar coordinates distance is determined by r, while the angle is measured by θ which need to be with respect to the x/axis. Determine any object by (r, θ). Do NOT forget: A+B = B+A A-B = A+(-B) A+(B+C)=(A+B)+C  Coordinate systems Negative & positive vectors Negative vector is a vector which will always be in the direction opposite the reference position direction.  Mass and Inertia Mass How hard is it for something to move Intimately related to the idea of inertia Distinct from weight, which relates to gravity. ❑ Mass is conserved, and can only be rearranged Inertia The property of an object that is at rest or in motion to remain at rest or in motion