FyU01, FyU03 - Mekanik HT2005 Lektioner ( = Föreläsningar + räkneövningar) Eva Lindroth [email protected], tel 08-5537 8616 Aktuell Information: http://www.atom.physto.se/~lindroth/mekanik05/mekanik05.html Inlämningsuppgifter: 75% ger 2 bonuspoäng på tentamen (3/10 -05). 60% ger 1 poämg. Omtentamen i januari. Laborationer 2 laborationer (Peter Lundin) + demonstrationer (Ulf Sassenberg) Didaktik [email protected]Kursbok: H. Benson, University Physics. Tabellverk: ( ALLA fysikkurser) Nordling och Österman: Physics Handbook (Studentlitteratur)
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http://www.physto.se/studentexpedition/Bibliotek: på plan 6 och 7, vardagar kl. 9 - 16, ingång via trappa från entréhallen; referens- och lånebibliotek (lånekort: legitimation + betald terminsräkning), läsplatserför studenter, datorer för e-tidskrifter, kopiator etc.
Studentexpedition
http://www.physto.se/afs/konto_student.html
Klassisk FysikMekanik ~ 1500 tal -1800 tal
Termodynamik ~ 1600 tal -1800 tal
Elektromagnetism ~ 1700 tal -1800 talFysik; materiens beståndsdelar och hur dessa
växelverkar med varandra. Experimentell vetenskap! Galilei 1564-1642
Newton 1642-1727
engelsk översättning:http://members.tripod.com/%7Egravitee/toc.htm
Original (latin) : http://dibinst.mit.edu/BURNDY/Collections/Babson/OnlineNewton/Principia.htm
Modern Fysik ~ 1900 tal -KvantmekanikRelativitetsteori
Principia 1:a utg. 1687
Modern Fysik- 100 år i år!
cdcandelaluminous intensitymolmoleamount of substanceKkelvinthermodynamic temperatureAampereelectric currentssecondtimekgkilogrammassmmeterlengthSymbolNameBase quantity
SI (Système International)
grundstorheter:
1 sekund, definieras som varaktigheten av 9192631770 perioder av den strålning som motsvarar övergången mellan de två hyperfinnivåerna i grundtillståndet hos atomen Cesium 133.
En meter är den sträcka som ljuset tillryggalägger i absolut vakuum under 1/299792458 sekund.
Storhet Mätetal Enhet
längd - 160 - cm
This international prototype, made of
platinum-iridium, is kept at the BIPM under
conditions specified by the 1st CGPM in 1889.
1 kg är definierat som massan av mass- prototypen (förvaras i Paris vid Bureau International
des Poids et Mesures(BIMP) http://www.bipm.org/ )
I Sverige: "Rikskilogrammet“, tillverkat samtidigt med den internationella prototypen
(90% platina och 10% iridium). Kalibrerades senast 1991:
0,999999965 kg med en mätosäkerhet på ±2,3 µg.
1. Definitioner från jordklotet; 1791: 1 m 10-7 av meridianens längd från ekvatorn, genom Paris, till Nordpolen
2. Prototypen utgör definitionen: 1889, gjordes en prototyp av platina och (10%) iridium. Längden skulle mätas vid given temperatur (isens smältpunkt) .
3. Definitionen skall utgå från en “lätt” mätbar fysikalisk konstant. 1960: baserades metern på våglängden av ljus som utsänds av krypton-86 (86Kr). Från 1983 är definitionen: Den sträcka som ljuset tillryggalägger i absolut vakuum under 1/299792458 sekund. Ljusets hastighet i vakuum är alltså numera definierad till exakt 299 792 458 m/s .
Enheten för längd – historik:
Standardisering i Sverige, historia:
1699, 1 enhets mil = 18000 alnar (= 10, 688 meter) innan dess var milen olika lång i olika landsändar. 1878 införs metersystemet.
Behovet av standardisering var stort, jmr. tex. viktenheten uns:
för guld var 1 uns = 27,9 g, för silver 1 uns = 26,3 g och som medicinalvikt 1 uns = 29,69 g. Motsvarande engelska enhet är 1 ounce (oz) = 28,35 g.
Dimensionsanalys:
marsvin
människa
häst
elefant
val
0.7
70
600
4000
15000
940
140
93
54
7
vikt (kg)äter/dygn/kg
kropsvikt (Joule)
L, M, T, tex. hastighet: LT-1, energi: ML2T-2
Massa ~ L3 däggdjur äter
huvudsakligen för att hålla värmen
svalnar genom ytan ~ L2
Bens bärkraft ~ L2
små djur (och barn) äter mer i relation till kroppsvikten
THEOREM II, PROPOSITION II The spaces described by a body falling from rest with a uniformly accelerated motion are to each other as the squares of the time-intervals employed in traversing these distances.
A piece of wooden moulding or scantling, about 12 cubits long, half a cubit wide, and three finger-breadths thick, was taken; on its edge was cut a channel a little more than one finger in breadth; having made this
groove very straight, smooth, and polished, and having lined it with parchment, also as smooth and polished as possible, we rolled along it a hard, smooth, and very round bronze ball. Having placed this
[213](179)
board in a sloping position, by lifting one end some one or two cubits above the other, we rolled the ball, as I was just saying, along the channel, noting, in a manner presently to be described, the time required to make
the descent. We repeated this experiment more than once in order to measure the time with an accuracy such that the deviation between two observations never exceeded one-tenth of a pulse-beat. Having
performed this operation and having assured ourselves of its reliability, we now rolled the ball only one-quarter the length of the channel; and having measured the time of its descent, we found it precisely one-half of the former. Next we tried other distances, comparing the time for the whole length with that for the
half, or with that for two-thirds, or three-fourths, or indeed for any fraction; in such experiments, repeated a full hundred times, we always found that the spaces traversed were to each other as the squares of the
times, and this was true for all inclinations of the plane, i. e., of the channel, along which we rolled the ball. We also observed that the times of descent, for various inclinations of the plane, bore to one another precisely that ratio which, as we shall see later, the Author had predicted and demonstrated for them.
For the measurement of time, we employed a large vessel of water placed in an elevated position; to the bottom of this vessel was soldered a pipe of small diameter giving a thin jet of water, which we collected in a small glass during the time of each descent, whether for the whole length of the channel or for a part of its
length; the water thus collected was weighed, after each descent, on a very accurate balance; the differences and ratios of these weights gave us the differences and ratios of the times, and this with such
accuracy that although the operation was repeated many, many times, there was no appreciable discrepancy in the results.