Introduction to Science

Conceptual Physics

Nature of ScienceScience

– views the universe as regular and predictable, not random and chaotic

– is about discovering explanations on how the universe works based on verifiable and testable evidence

– Evidence should be coupled with reason, logic, and skepticism.

A Search for Patterns The human mind seeks

order. Our first explanations of

nature were based on spiritual beliefs.

Later, the ancient Greeks, Chinese, & Persians searched for patterns in nature.

Consistency in patterns must be governed by basic principals.

Understanding these principals gives us the power of prediction.

Observation and Technology Science helps us

understand how the universe works.

In the pursuit of “how” questions, science leads to the production of technology.

Technological advances help us make new observations of the universe.

Science and technology leapfrog each other, each making advances in the other possible.

The Basic Science The study of science today branches into the

study of living and non-living things. Life Sciences

– Biology, Zoology, Botany Physical Sciences

– Geology, Astronomy, Chemistry

– Physics Physics is the most basic science

– Motion, Forces, Energy, Matter, Heat, Sound, Light, and the composition of atoms

– All other sciences rely on an understanding of Physics.

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Scientific Methods

The Scientific Method

Levels of Confidence Experiments repeated with the same results by

multiple people over time lead to hypotheses with a high degree of confidence.

Hypotheses with a high degree of confidence can be elevated to the status of theory, or a statement with extremely high confidence.

A scientific law states a repeated observation about nature.

Models (or analogues) are used in science to represent things in nature that are too big, small, or complex to study easily.

Mathematical models (equations) are used to make predictions about natural phenomena.

Science Has Limits The phenomenon must be testable. No knowledge is absolute.

– What we believe to be true today may be obsolete tomorrow.

Science does not prove anything, only gives evidence to support a claim.

Science can’t answer all questions.– Science answers “how” questions.

• How did the universe begin?

– “Why” questions are out of the bounds of science and should be left to philosophers.

• Why is there a universe?

Qualitative vs. Quantitative Many theories and laws

can be described using mathematics.

Qualitative statements describe observations seen in the universe.

Quantitative statements are mathematical equations that describe scientific theories and laws.

Units of Measurement Mathematics is the language of science.

Measurements give scientists the values used in the formulas that describe nature quantitatively.

All scientists need a consistent system of measurement in order to communicate their ideas and discoveries.

The International System of Units (SI) is used throughout the world.

SI Base Units in Physics Length- METER Mass- KILOGRAM Time- SECOND Temperature-

KELVIN Electric Current-

AMPERE Amount of

Substance- MOLE Luminous Intensity-

CANDELA

SI Units

Combinations of base units are called derived units.– Area (l • w) {units ex.: m • m = m2}

– Volume (l • w • h) {units ex.: m • m • m = m3}

– Pressure (F ⁄ A) {units ex.: N ⁄ m2}

• Pressure unit is called the Pascal

– Force (m • a) {units ex.: kg • m ⁄ s2}

• Force unit is called the Newton

• Weight is an example of force

– Speed (d ⁄ t) {units ex.: m ⁄ s}

Metric System- multiples of ten

Now that’s just silly!

Prefixes Used For Large Measurements KILO- thousand

– Times 1,000 or 103

MEGA- million– Times 1,000,000 or

106

GIGA- billion – Times 1,000,000,000

or 109

Prefixes Used for Small Measurements

DECI- tenth– Times 0.1 or 10-1

CENTI- Hundredth– Times 0.01 or 10-2

MILLI- thousandth– Times 0.001 or 10-3

MICRO- millionth– Times 0.000 001 or

10-6

NANO- billionth– Times 0.000 000 001

or 10-9

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http://physics.nist.gov/cuu/Units/prefixes.html

Scientific Notation Used to write very large and very small numbers

pattern: a x 10b

a is the coefficient, (AKA the mantissa) b is the exponent

The mantissa must be 1 or greater and less than 10 (digits 1–9).

The exponent is determined by how many places the decimal must be moved when converting into scientific notation.

The Earth’s mass is about 5,973,600,000,000,000,000,000,000 kg

In scientific notation it is written 5.9736 x 1024 kg

Scientific Notation Practice

10000

0.001

4081973.701

4 600 000 000 000

102

10-2

1.5 x 105

300.00

1 x 104

1 x 10-3

4.081973701 x 106

4.6 x 1012

100

0.01

150 000

3.0000 x 102

Unit Conversion Conversion factor- a fraction that is

mathematically equivalent to 1 that relates two different units (both must be same kind of unit (e.g. length, mass, etc.))– Numerator and denominator represent the same thing in

two different units– E.g. 12 in ⁄ 1 ft; 1 m ⁄ 3.3 ft

Converting to a larger unit results in a smaller number (e.g. 234 m = 0.234 km)

RULES: 1. Start with what you are given and put it over 1 2. Multiply by the conversion factor to cancel out

the units you begin with and work toward the units you want

Convert 4.08 meters to centimeters

– 408 cm = 4.08 x 102 cm

Convert 13 milliseconds to seconds

– 13 ms = 13 x 10–3 s = 1.3 x 10–2 s

Convert 15 megaamperes to amperes

– 15 MA = 15 x 106 A = 1.5 x 107 A

Convert 875 gigagrams to nanograms

– 875 x 109 g = 8.75 x 1011 g = 8.75 x 1020 ng

Unit Conversion Practice

Organizing Data Line Graphs– Best for displaying

data that change– Easy to see trends

Two variables– Independent

• X-axis

– Dependent• Y-axis

Title, axes labeled, units included– Reader should be

able to understand what took place in the experiment by looking at the graph

Organizing Data

Bar Graphs– Best for

comparing data Makes differences

in values more clear to the reader

Title, axes labeled, units included

Organizing Data Pie charts– Best for

displaying data that are parts of a whole

– Percentages Title, legend,

data

Graphing Terminology Line of Best Fit (LOBF)

– Shows the trend of the plotted points– Draw the line over as many points as possible with the

same number of points balanced above and below the ruler

Extrapolate– Constructing new data points outside the data set plotted– Extend the line of best fit

Linear vs. non-linear– Straight line vs. curved line

Slope– Pick two points on the LOBF far from each other.– Calculate rise ⁄ run (difference in y values divided by

difference in x values).y2-y1 / x2-x1

Experimentation and Graphing Constant- only ONE variable is changed Variable-

– Independent- the variable that is manipulated (systematically changed)

• X-axis

– Dependent- any change that results from manipulating the independent variable

• Y-axis– DRY MIX

Dependent variable depends on the independent variable

Control- a sample that is treated exactly like the experimental group except that the independent variable is not manipulated

Direct and Inverse Relationships In math or statistics,

a direct relationship is a relationship between two variables in which they both increase or decrease in conjunction

In this example, an increase in x results in an increase in y

Direct and Inverse Relationships

In math or statistics, an inverse relationship is a relationship between variables in which one variable decreases as the other increases

In this example, an increase in x results in a decrease in y

Accuracy vs. Precision

Accuracy- how close a measured value is to its accepted, or true, value

Precision- how close a series of measurements are to one another

Bull’s eye of the target will be considered the true value

Examples Good accuracy

Good precision

Poor accuracyGood precision

Good accuracyPoor precision

Poor accuracyPoor precision

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Accuracy vs. Precision

true value

accurate butnot precise

preciseandaccurate

not precise,not accurate

precise butnot accurate

Three Sources of ErrorRandom Error

– Fluctuation in measurements about some value–sometimes larger, sometimes smaller

– Cancels out, on average, with many valuesSystematic Error

– Due to mis-calibrated instrument or one with a zero error

Reading Error– Error in measurement inherent to measuring

instrument (e.g. ± 1 mm with a meterstick)

Review question:

The following measurements were made for the density of lead. Each student measured their piece of lead three times:

Rachel: 11.32 g/ml, 11.35 g/ml, 11.33 g/mlDaniel: 11.43 g/ml, 11.44 g/ml, 11.42 g/mlRobert: 11.55 g/ml, 11.34 g/ml, 11.04 g/mlThe actual density of lead is 11.34 g/ml.

Which person’s measurements were the most accurate? Which were precise? Which were both accurate and precise?