Physics 3A 1st Half
Chapter 1: Introduction, Units, Measurements and Vectors Know more complex trigonometry.
"Not important so much"
Chapter 1: Introduction, Units, Measurements and Vectors Dimensional analysis problems. Find the dimension of: a) velocity b) acceleration c) force d) linear momentum e) work
* dimension = physical dimension
Chapter 1: Introduction, Units, Measurements and Vectors What is the purpose of giving numerical values for physical quantities, and equations for physical principles? * How can physical quantities be expressed? - Define both.
Giving numerical values for physical quantities and equations for physical principles allows us to understand nature much more deeply than qualitative descriptions alone. * To comprehend these vast ranges, we must also have accepted units in which to express them. * All physical quantities can be expressed as combinations of only seven base quantities. Physical Quantity: Characteristic or property of an object that can be measured or calculated from other measurements. * Length, area, volume, mass, weight, time, temperature, force, linear momentum, electric field, gravitational field,... Base Quantity: Physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them; * Length, mass, time, electrical current, temperature, amount of substance, luminous intensity.
Chapter 1: Introduction, Units, Measurements and Vectors What is the Order of Magnitude? * How do you find it?
Giving the order of magnitude of a number is the power of 10 that most closely approximates it. Thus, the order of magnitude refers to the scale (or size) of a value. * Each power of 10 represents a different order of magnitude. EX: 10^1 10^2 10^3 10^0 10^-1 * To find the order of magnitude of a number, take the base-10 logarithm of the number and round it to the nearest integer, then the order of magnitude of the number is simply the resulting power of 10. The order of magnitude of 800 is 10^3 because log10(800)=2.903, which rounds to 3. The order of magnitude of 450 is 10^3 because log10(450)=2.653 which rounds to 3 as well.
Chapter 1: Introduction, Units, Measurements and Vectors What is the Language of Physics?
Mathematics
Chapter 1: Introduction, Units, Measurements and Vectors Is there an Ultimate Theory, Theory of Everything (TOE)?
Maybe! Not yet! We don't know! The goal of physics is to find the TOE!
Chapter 1: Introduction, Units, Measurements and Vectors What does Observation mean in physics?
Observations in physics are defined as experiments based on accurate and precise measurements.
Chapter 1: Introduction, Units, Measurements and Vectors What are the steps in physics?
1. Observing phenomena: (measurements, units) 2. Finding/constructing a theory/model: (principles, laws, mathematical structure) 3. Test the theory/model with more accurate and precise experiments: (more accurate measurements and units)
Chapter 1: Introduction, Units, Measurements and Vectors What does Model mean in physics?
A "model" is a representation of something that is often too difficult (or impossible) to display directly. Although a model is justified by experimental tests, it is only accurate in describing certain aspects of a physical system and is based on a theory. * Theories may include or may not include some models. * Models skip over many details to provide a big picture understanding. * A model is a simplified description of reality that is used to reduce the complexity of a problem so it can be analyzed and understood. * Models simplify complex situations. * Stripping away the details to focus on essential features is a process called modeling. A model is a simplified picture of reality, but one that still captures the essence of what we want to study. Thus, "mass on a spring" is a model of almost all oscillating systems. Models allow us to make sense of complex situations by providing framework for thinking about them.
Chapter 1: Introduction, Units, Measurements and Vectors What does Theory mean in physics?
A set of some fundamental concepts, assumptions (principles) and rules (laws) supported by a mathematical structure that is able to explain a wide range of phenomena is called a "theory" which is testable and verified multiple times by various groups of researchers.
Chapter 1: Introduction, Units, Measurements and Vectors Define and compare accuracy and precision.
Accuracy and Precision of a Measurement: Science is based on observation and experiment - that is, on measurements. * Accuracy is how close a measurement is to the accepted reference value for that measurement. * Precision of measurements refers to how close the agreement is between repeated independent measurements (which are repeated under the same conditions). The precision of a measuring system is related to the uncertainty in the measurements where as the accuracy is related to the discrepancy from the accepted reference value.
Chapter 1: Introduction, Units, Measurements and Vectors What is the meaning of Understanding in physics?
In physics, we can say we "understand" some phenomena when we have a good model or theory to explain it. * Having a lot of things explain the same phenomena is not a good model. Ex: The floor attracts marker. The desk attracts marker. Make more general, a lot of things attract the marker when you drop it.
Chapter 1: Introduction, Units, Measurements and Vectors Be familiar with unit conversions and know how to do unit conversion problems.
Know how to do this.
Chapter 1: Introduction, Units, Measurements and Vectors Unit conversion problems:
Know how to do this.
Chapter 1: Introduction, Units, Measurements and Vectors What is the metric system?
Metric system: SI units are part of the metric system, in which the units are categorized by factors of 10.
Chapter 1: Introduction, Units, Measurements and Vectors What is physics?
Physics is the way to understanding the Nature: * How do the things at all scales (from sub atomic scales to entire universe) work? * What are the laws of nature? * Which phenomena-explanation (theory/model) is better and which one is the best one?
Chapter 1: Introduction, Units, Measurements and Vectors Understand Dimensional Analysis and its importance.
The dimension of any physical quantity expresses its dependence on the base quantities as a product of symbols (or powers of symbols) representing the base quantities. * Remember: you need consistent units, (you can't add apples and oranges). For example, a measurement of length is said to have dimension L or L^1, a measurement of mass has dimension M or M^1, and a measurement of time has dimension T or T^1. Like units, dimensions obey the rules of algebra. Thus, area is the product of two lengths and so has dimension L^2, or length squared (volume = l x w x h = L x L x L = L^3, unit: m^3 but dimension = L^3). EX: * Physical dimension: lengths * Units: inch, centimeter, meter, etc. The importance of the concept of dimension arises from the fact that any mathematical equation relating physical quantities must be dimensionally consistent, which means the equation must obey the following rules: * Every term in an expression must have the same dimensions; it does not make sense to add or subtract quantities of different dimension. In particular, the expressions on each side of the equality in an equation must have the same dimensions. * The arguments of any of the standard mathematical functions such as trigonometric functions (such as sine and cosine), logarithms, or exponential functions that appear in the equation must be dimensionless. These functions require pure numbers as inputs and give pure numbers as outputs.
Chapter 1: Introduction, Units, Measurements and Vectors Define: * Units * Base unit * SI units
Units: standards used for expressing and comparing measurements. Base unit: standard for expressing the measurement of a base quantity within a particular system of units; defined by a particular procedure used to measure the corresponding base quantity. SI units: the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams.
Chapter 1: Introduction, Units, Measurements and Vectors What is a good (better) model/theory in physics?
We say a model/theory is a good one when it is able to explain more phenomena with less fundamental assumptions (principles).
