Why study science, especially physics?

“That is, an ordering of the world around us.” Doug Giancoli What do you see? Constellation Pleiades

What is physics? Science is built up with facts as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house. Jules Henri Poincaré 1903 Physics is the study of the most fundamental interactions between time, space, energy and matter. VCU Department of Physics

Physics in action

Science develops through the use of hypotheses, models, and theories. Explanations of how things work. Sometimes observations lead to laws that describe the nature of the physical world.

An hypothesis, an educated guess, is often based on what is already known about a given question and forms the basis for experiments that lead to new understanding. In the early 60’s Sheldon Lee Glashow proposed that the proton was made of smaller particles.

A scientific hypothesis or theory must be testable. It must be possible in principle to prove it wrong. This criterion comes primarily from the work of the philosopher of science Karl Popper, and is called "falsifiability” You must be able to prove that an incorrect hypothesis is wrong.

Examples of Non-Falsifiable Statements An alien spaceship crashed in Roswell New Mexico. A giant white gorilla lives in the Himalayan mountains. Loch Ness contains a giant reptile.

Examples of Falsifiable Statements No alien spaceships have ever landed in Roswell New Mexico. This critter (just pulled from Loch Ness) is a fish.

(A)(A) There is intelligent life on other stars. (B) The Moon is made entirely of cheese. (C) Isaac Newton was the greatest scientist. (D) There is beauty in a sunset. (E) There is cheese on the Moon. (B) (C) (D) (E)

(A)(A) The Minoans were the first civilization on Crete. (B) The Minoans were the best civilization on Crete. (C) The Minoans were not the first civilization on Crete. (D) The Minoans were not the best civilization on Crete. (E) The Minoans were a civilization on Crete. (B) (C) (D) (E)

An important difference between science and other creative activities is that science requires testing to see if a theory’s predictions are born out by experiment. Atlas Detector

Testing is always necessary and often difficult in physics. Suppermassive Black hole?

Model A kind of analogy or mental image of a phenomena in terms of something we are already familiar with. Example: Planetary model of the atom

Theory A reasonable explanation of observed events that are related. A theory may involve a model. Example: Quantum Theory I started it but I don't believe it's real.

“Theories are never derived directly from observations - they are created to explain observations.” Douglas Giancoli Theory of Relativity. My time is not necessarily your time.

Law or Principle A statement that describes the relationship between various phenomena. Example: Universal Law of Gravitation Newton had no idea What causes gravity?

There is no such thing as absolute certainty in science. Important announcement

Questioning is a vital part of physics and all sciences.

Every sentence I utter must be understood not as an affirmation, but as a question. Niels Bohr

I know not what I appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell, whilest the great ocean of truth lay all undiscovered before me. If I have been able to see further, it was only because I stood on the shoulders of giants.

Quick Lab Spinners

The basic basics Some math stuff

And now we begin.

Units of Measure: Physics uses the International System of Units (SI) to measure most physical quantities and perform most of its calculations.

Fundamental Units UnitQuantity meter (m)length kilogram (kg)mass second (s)time ampere (A)electric current Kelvin (K)temperature mole (mol)amount of sub. candela (cd)luminous int.

meter (m)length kilogram (kg)mass second (s)time These three units make up a subset call the MKS system.

A derived unit is a combination of fundamental units. m/s 2 Kgm/s 2 Units like cm or m 3 are not derived units.

All units except the kilogram are defined in terms of natural phenomena. The kilogram is the mass of a platinum-iridium metal cylinder.

Slide 36 Fig. 1.1a, p.4

1 meter is the distance light travels in 1/ second in a vacuum. 1 second is the time for vibrations of a cesium-133 atom Unit definitions:

Slide 38 Fig. 1.1b, p.4 Cascade Atomic Clock

Conversions! WOOOO HOOOOO! But first a video

Metric or SI prefixes Prefixsymbolx from 10 x yottaY241,000,000,000,000,000,000,000,000 zettaZ211,000,000,000,000,000,000,000 exaE181,000,000,000,000,000,000 petaP151,000,000,000,000,000 teraT121,000,000,000,000 gigaG91,000,000,000 megaM61,000,000 kilok31,000 hectoh2100 decada110 base01 decid0.1 centic millim microμ nanon picop femtof attoa zeptoz yoctoy

Conversion Lab

All measurements are subject to uncertainty. These can be due to the expertise of the investigator, the instrument, and parallax.

Parallax is the apparent shift in the position of an object when it is viewed from various angles.

Precision Precision is the degree of exactness to which the measurement of a quantity can be reproduced.

Precision is also the agreement among several measurements that have been made in the same way. Deviation is used to report precision.

Accuracy The extent to which a measured value agrees with the standard value of a quantity. Accuracy is reported with relative error.

Relative Error Error Calculations: E r -- Relative Error O -- Observed Value A -- Accepted Value

Significant digits are all the digits that are certain plus a digit that estimates the fraction of the smallest division on the measuring scale. Significant Digits

Rules of significance:  Nonzero digits are always significant has 4 significant digits  All final zeros after the decimal point are significant has 5 significant digits

 Zeros between two other significant digits are always significant has 5 significant digits has 4 significant digits

 Zeros used solely for spacing the decimal point are not significant has 1 significant digit

How many significant figures [digits] are in the following values? X

Operations with significant digits The result of any mathematical operation with measurements can never be more precise than the least precise measurement.

In multiplication and division the factor with the least number of significant digits determines the significance of the answer / = Answer is rounded to 8.15

In addition and subtraction the least precise measurement determines the precision of the answer =

Do the addition

12.06 X X X

What is scientific Notation? Scientific notation is a way of expressing really big numbers or really small numbers. It is most often used in “scientific” calculations where the analysis must be very precise. Scientific Notation slides from presentation by Jenny Erickson

Scientific notation consists of two parts: A number between 1 and 10 A power of 10 N x 10 x

Changing standard form to scientific notation.

To change standard form to scientific notation… Place the decimal point so that there is one non-zero digit to the left of the decimal point. Count the number of decimal places the decimal point has “moved” from the original number. This will be the exponent on the 10.

Continued… If the original number was less than 1, then the exponent is negative. If the original number was greater than 1, then the exponent is positive.

Example 1 Given: 289,800,000 Use: (moved 8 places) Answer: x 10 8

Example 2 Given: Use: 5.67 (moved 4 places) Answer: 5.67 x 10 -4

To change scientific notation to standard form… Simply move the decimal point to the right for positive exponent 10. Move the decimal point to the left for negative exponent 10. (Use zeros to fill in places.)

Example 3 Given: x 10 6 Answer: 5,093,000 (moved 6 places to the right)

Example 4 Given: x Answer: (moved 4 places to the left)

Conversions! WOOOO HOOOOO!

Metric or SI prefixes Prefixsymbolx from 10 x yottaY241,000,000,000,000,000,000,000,000 zettaZ211,000,000,000,000,000,000,000 exaE181,000,000,000,000,000,000 petaP151,000,000,000,000,000 teraT121,000,000,000,000 gigaG91,000,000,000 megaM61,000,000 kilok31,000 hectoh2100 decada110 base01 decid0.1 centic millim microμ nanon picop femtof attoa zeptoz yoctoy

Conversion Lab

Graphical Relationships  Linear  Quadratic  Inverse

y x Linear relationships have the form y=mx+b

Y X ΔyΔy ΔxΔx m is the slope m = ∆ y/ ∆ x b is the y intercept

Y X Inverse relationships have the form xy = k or y = k/x

Y X The graph of an Inverse is a hyperbola.

Y X Quadratic relationships have the form y = kx 2

Y X The graph of a Quadratic relationships is a parabola.

Quiz!!! PrefixPower of

1. 12 km to m mL to L Kg to g E.C = ? E.C. 2. (1000)(2.0) = ?

What is physics