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 PhysicsName 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(pre-research)

Hypothesis Experiment

Independent and dependent variableControlled 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.

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.

a. 50.3m has three sig figs

b. 3.0025s has five sig figs

2. Zeros in front of nonzero digits are not significant.

a. 0.892kg has three sig figs

b. 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.

a. 57.00g has four significant figures.

b. 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)

a. 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.

b. 20m may contain one or two significant figures, but we will assume it has one sig fig.

Significant FiguresType 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+5.85103.15

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.

123X 5.35658.05

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:a) 6.20 mg in kg

b) 3 x 10-9 s in ms

c) 88.0 km in m

PRACTICE!

Perform these calculations, following the rules for significant figures.a) 26 x 0.02584

b) 15.3 ÷ 1.1

c) 782.45 – 3.5328

d) 63.258 + 734.2

Measurement Lab

Follow Directions!

1.3

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 PhysicsQuantity 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.