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Learning Physics

In our School: courses FY01-FY07+FY08 +FY-FY11 FY01-03 (1. y); FY03-FY06 (2. y); FY07 (3.y);

FY08 (preparing to matriculation examination, 3. y)

FY9 (project course)

FY10 (eximia course)

Further studies in Universities

Occupations Physicians (research work)

Engineers

Medicine (doctors, ..)

Teachers (upper sec, vocational s, universities, institutions)

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Physics

exact Natural Science

learns Us to understand Natural Phenomena

experimental science (Empirical),

measuring as accurate as possible, makingMathematical models (Exact Science) andformulas and having Theorethical discuss.

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Historical overwiew

Natural Philosophy Timeline Ancient Science Astronomy 2900BC

Astronomy, Sun and Moon, planetstechnical devices: hunting, fishing, agriculture, building

Antic Science Astronomy 400BC beginning of Science at 1500BC, philosophical thinking and discussing Pythagoras 500BC, Platon 400BC, Aristotle 250BC: Earth, Fire, Water, Air, Ether

Early Middle Age Science Astronomy, Alchemy, Mathematics 1100 respect of Aristotle: Earth is in the middle Alchemistry: ancient art of obscure origin that sought to transform

base metals (e.g., lead) into silver and gold; forerunner of the scienceof chemistry

Universities arise in Italy, France, Spain and England in the late11th and the 12th centuries for the study of arts, law, medicine, andtheology

Copernikus 1500 Renaissance astronomer and the first person toformulate a comprehensive heliocentric cosmology which displacedthe Earth from the center of the universe.

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Classical Physics 1500- Research became important ENERGY thinking arises Thermometer, electric phenomena, speed of light is constant, X-rays Different parts of Physics have connections to each other Galilei 1564-1642: Beginning of Classical Physics Newton 1642-1727: Law of Gravitation: Principia Mathematica Philosophie

Naturalis Ampere 1775-1836: connection between electricity and magnetism

Mechanics Thermal Physics Wave Motion Acoustics Light and Optics Electricity and Magnetism

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Modern Physics 1900-

Classical Physics could not explain the atomic structure of the matter The basic particles of the matter have both particle- and waveform

(Dualism) E=mc2

Laws of Mechanics are working when the velocity is small Albert Einstein, Theory of relativity:

The speed of light in vacuum is constant (c=2,99792458*108 m/s) All motion is relative. The spectator can not determine by Physical

experiment, if he/she is in rest or in constant, direct motion.

Edwin Hubble 1924: there exists other galaxies than Milky Way Wilhelm Röntgen X-rays Marie Curie Radioactivity

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Parts of Physics

Mechanics Motion of particles, balance of particles: Measuring, Velocity, Force, Acceleration, Force and Motion,

Newton’s laws, Energy, …. On of the most important part of Physics: Galileo, Newton

Thermal Physics Temperature, Thermal Energy, Phases, Thermal Machines

Acoustics Sound waves, Technical devices

Optics Mirrors, Lenses, Optical devices, Light in different matters and boundaries, Diffraction

Electromagnetism Electricity, Magnetism, Electric Charge and Current, Resistance, Electric

Potential, Power Electric and Magnetic Field, Generators, Electric motors

Modern Physics Theory of Relativity

Gravitation, structure of time-space

Quantum Mechanics Structure of Atoms, Radioactivity, Nuclear Physics

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Measuring and measuring accuracy

Quantity (=suure) Quality of particle or material that can be measured

Quantity= numerical value * unit

Example: speed = 90 km/h; length = 285,4 m; time = 0,4 s

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Measuring and accuracy

There is uncertainty associated with every measurement,and the Uncertainty arises from different sources:• the limited accuracy of every measuring instrument,• when reading the instrument,• the measuring instrument is affecting the

circumstances,

• marking errors etc.

NOTICE•the result of a measurement is an approximation.•if you measure the value of the quantity many times, youget a group of results, from where you can decide the mostlikely value for the unit.

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Error types when measuring

Rough errorSystematic errorOccasional error

NOTICE•the result of a measurement is an approximation.•if you measure the value of the quantity many times, youget a group of results, from where you can decide the mostlikely value for the unit.

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Calculations in Physics

All the measuring results are approximations (not”exact”), so we must approximate the answers withcertain rules.

The rules are different in the cases where we have justadding/substracting or also multipliying/dividing in theformula.

DefinitionSignificant numbers (merkitsevät numerot)

All numbers are significant except

zeros at the end of an integer (mostly)

Zeros at the beginning of a decimal number

ExamplesTell the Amount of Significant Numbers

7,60 s

0,0867 m

100g

200 MB

1,51.106 m

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Digits in calculationsWhen making measurements, or when doing calculations, you should avoid the temptation to keep more digits inthe final answer than is justified (or allowed).

Multiplying and dividing

Example:The area of rectangle (These are measuring results!)

Length=6,8cm A1=6,7x11,2=75,04Height=11.3 cmArea A= 76,84 cm2 A2=6,9x11,4=78,66The real area is between 75,04 and 78,66, so you cannot use the precision of0,01cm2. The best answer should be 77cm2 and the uncertainty is 1-2 cm2 . The twodigits must be dropped, because those are not significant digits.

The final result of multiplication or division should haveonly as many digits as the number with the least numberof significant figures (numbers) used in the calculation.

11,3

6,8

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Digits in calculations

Adding and subtractingExample:

Measuring results of length are 7,56 cm and 3,6 cm. The sum is 11,16 cm but it is not right to usethe accuracy of 0,01. At the end of calculation you must approximate the result to 11,2cm.

The final result cannot be more accurate than the least accurate number used. Here we count theleast accurate number with decimals (how many numbers is after decimal point).

The final result of addition or subtraction shouldhave only as many digits after the decimal pointas the number with the least number of digitsafter decimal point used in the calculation.

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Measuring devices for lengthHistorical:Scale (weight)Ruler, Caliper ruler (length, thickness)Micrometer screw (thickness)Modern:Laser (length)Ultrahigh sound (thickness)

and for timeStopwatch vs. Lightports

Examples Measuring of lengthMeasuring of time

Q Is possible to make the uncertainty of themeasurement smaller?

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Measured quantity x can be given in form

x = xm +Δx

wherexm= result of measurementΔx= absolute error due to the used device (uncertainty)

The accurate result of the measurement is betweenxm + Δx and xm – Δx.

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Example 1 Is the diamond yours?

A Friend asks you to borrow your precious

diamond for a day to show her family. You are abit worried so you carefully have your diamondweighted on a scale which reads 8,17g. Thescale’s accuracy is claimed to be +0,05g. Thenext day you weigh the returned diamond

again, getting 8,09g. Is it your diamond?

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Error analysis in experiments1. Mathematical analysis with the average deviation

Count the average value of measuring results

Count the absolute deviation of each measuring result AND withthese count the Average absolute deviation

Count the av

The result with errorlimits is then

AVERAGE VALUE +-AVERAGE absolute DEVIATION

2. Verbal Analysis of the uncertainty

the limited accuracy of every measuring instrument, whenreading the instrument, the measuring instrument isaffecting the circumstances, marking errors etc.

Measuring and error limits

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Measuring and Work report

Physics is experimental science. After making experiments we also make workreports from the research.

The contents of the work report is following (example)

the theory of the phenomena

choosing the measuring target

measuring plan, devices and methods in the research

results of measurements

results and a graphic illustration

estimation of error

the study of the work and results

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SI-system

accepted in Finland 1975

International agreement of Quantities and Units whichare used

Includes Basic Quantities and Units

Definition of standard units

Derived Quantities and Units

Derived from basic units

Additional Quantities and Units

Prefixes

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SI basic quantitiesand units

SI Base quantity, symbol Name Symbol

length, l or s meter m

mass, m kilogram  kg

time, t second s

electric current, I ampere Athermodynamic

temperature , T       kelvin K

amount of substance, n mole mol

luminous intensity, I candela cd

SI base unit

SI quantities and the definions of the Quantities can be found from yourTablebook (MAOL)

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Units outside the SI

•additional units

•here you can seesome exampels

•more from yourMAOL

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SI derived quantities and units

•Other quantities, called derived quantities, are defined interms of the seven base quantities via a system of quantityequations.

•The SI derived units for these derived quantities areobtained from these equations and the seven SI baseunits.

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Examples of SI derived units

SI derived unit

Derived quantity Name Symbol

area square meter m2

volume cubic meter m3

speed, velocity meter per second m/s

acceleration meter per second squared m/s2

density kilogram per cubic meter kg/m3

amount-of-substanceconcentration

mole per cubic meter mol/m3

luminance candela per square meter cd/m2

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Counting with Quantities From quantity equations you can find equation for the asked

quantity

Ex1. Force F, body mass m and aceeleration a are depending fromeach other by equation F=ma.

Make equation for counting m and a.

Ex2. Equation s=vt are telling how trip, velocityand time aredepending from each other.

A car is travelling 58km in 50 minutes. Count the average speed ofthe car.