Physics 1.1

Physics Physics is a branch of science that involves the study of the physical world: energy, matter, and how they are related.

Areas Within Physics Name Subjects Examples Mechanics Motion and its causes Falling objects, friction, weight, spinning objects Thermodynamics Heat and temperature Melting and freezing processes, engines, refrigerators Vibrations and wave phenomena Specific types of repetitive motions Springs, pendulums, sound Optics Light Mirrors, lenses, color, astronomy Electromagnetism Electricity, magnetism, and light Electrical charge, circuitry, permanent magnets, electromagnets Relativity Particles moving at any speed, including very high speeds Particle collisions, particle accelerators, nuclear energy Quantum mechanics Behavior of submicroscopic particles The atom and its parts

Physics Best Friend? THE SCIENTIFIC METHOD!

Scientific Method

Scientific Method Observation Hypothesis Experiment (pre-research) Hypothesis Experiment Independent and dependent variable Controlled experiment Results - data , graphs, tables, etc. Conclusion – is hypothesis supported?

Importance of Models Physicists often use simple models to explain the most fundamental features of various phenomena, because it is basically impossible to describe all aspects at the same time.

Importance of Models Physicist break the phenomena down into different parts, decide which parts are important to what they want to study, and disregard the rest.

Models and Experiments Models help guide experimental design by focusing what you are testing and keeping all other variables the same. This is an example of a controlled experiment, where you change only one variable.

Measurements in Experiments 1.2

Numbers as Measurements Systeme International (SI) is a system of units used for measurements by scientists all around the world. Why do we all use the same system?

SI Units

Prefixes Used with SI Units

Scientific Notation Scientific notation is a way we show large and small numbers. The measurement is recorded to a power of 10, and all of the figures given are significant. EX: c = 3.00 x 108 m/s = 1 sig fig (3)

Uncertainty in Measurements Results are often reported with an uncertainty to allow for a minimal difference in measurement readings. Ex: 14.6 ± 0.2 cm. --- the reading can be anywhere between 14.4cm and 14.8cm. The larger the uncertainty, the less the precision.

Accuracy vs. Precision Accuracy describes how close a measurement is to reality. Precision describes the limitations of the measuring device used.

Significant Figures Significant figures are used to indicate precision ( the degree of exactness of a measurement). In calculations, the number of significant figures in your result depends on the number of significant figures in each measurement.

Rule Examples 1. Zeros between other nonzero digits are significant. 50.3m has three sig figs 3.0025s has five sig figs 2. Zeros in front of nonzero digits are not significant. 0.892kg has three sig figs 0.0008ms has one sig fig 3. Zeros that are at the end of a number and also to the right of the decimal are significant. 57.00g has four significant figures. 2.000000kg has seven sig figs 4. Zeros at the end of a number but to the left of a decimal are significant if they have been measured or are the first estimated digit; otherwise, they are not significant. (we treat them as not significant) 1000m may contain from one to four significant figures, depending on the precision of the measurement, but we will be assumed that measurements like this have one significant figure. 20m may contain one or two significant figures, but we will assume it has one sig fig.

Significant Figures Type of Calculation Rule Example Addition or subtraction The final answer should have the same number of digits to the right of the decimal as the measurement with the smallest number of digits to the right of the decimal. 97.3 +5.85 103.15 Round off to 103.2 Multiplication or division The final answer has the same number of significant figures as the measurement having the smallest number of significant figures. 123 X 5.35 658.05 Round off to 658

Significant Figures Calculators do not pay attention to significant figures. Calculators often exaggerate the precision of your final results by returning answers with as many digits as the display can show.

PRACTICE! 1. Convert the following measurements: 6.20 mg in kg 3 x 10-9 s in ms 88.0 km in m

PRACTICE! Perform these calculations, following the rules for significant figures. 26 x 0.02584 15.3 ÷ 1.1 782.45 – 3.5328 63.258 + 734.2

Measurement Lab Follow Directions!

The language of physics 1.3 The language of physics

Mathematics and Physics Tables, graphs, and equations can make data easier to understand. Physics equations indicate relationships through variables. Variables and other specific quantities are abbreviated with letters that are boldfaced or italicized.

Mathematics and Physics Quantity Symbol Units Unit Abbreviations Change in position Δx, Δy Meters m Time interval Δt Seconds s Mass M Kilograms kg

Evaluating Expressions Dimensional analysis can weed out invalid equations. Treating the units as algebraic quantities, which can be cancelled, is called dimensional analysis. EX: quantities can be added or subtracted only if they have the same dimensions. Its used in choosing conversion factors (a multiplier equal to 1).

PRACTICE! 1. How many megahertz is 750 kilohertz? 2. Convert 5021 centimeters to kilometers. 3. How many seconds are in a leap year (1 extra day)? 4. Convert the speed 5.30 m/s to km/h.