Orbita

Kao pojam u fizici, orbita je put koje jedno tijelo čini oko drugog tijela dok je pod utjecajem neke sile. Category:Fizika

Sila

Sila je jedan od najelementarnijih pojmova u fizici. To je vektorska veličina (određena je pravcem, smjerom i iznosom) kojom opisujemo međudjelovanje tijela i njegove okoline i kojom objašnjavamo uzroke gibanja. SI jedinica za silu je njutn čija je oznaka N (nazvana tako prema Isaacu Newtonu). Osnovna podjela sila:
- Kontaktne - kako im i samo ime govori, rezultat su fizičkog kontakta dvaju tijela. Informacija o djelovanju neke kontaktne sile se sustavom prenosi mijenjanjem međumolekulskih razmaka u strukturi materijala. Mogu djelovati koncentrirano u nekoj točki, na nekoj liniji ili na površini (kada ih se može predstaviti kao tlak). Postoji više vrsta kontaktnih sila;
- aktivne - npr. sila kojom reket udara tenisku lopticu
- reaktivne - npr. sila kojom na nas djeluje podloga na kojoj stojimo
- vanjske - sve kontaktne sile koje na neki sustav djeluju izvana
- unutarnje - sile međudjelovanja elemenata unutar nekog sustava, npr. naprezanje u materijalu
- Volumenske (masene) - vezane su uz postojanje polja sila u nekom prostoru. One ne djeluju neposredno na neki dio tijela, a na ostale dijelove posredno, već istovremeno djeluju na sve čestice tijela, tj. prožimaju ga u njegovom cijelom volumenu. U ovu vrstu sila spadaju elektromagnetske, gravitacijska, inercijalne sile. Elektromagnetske i gravitacijske sile su uvijek aktivne sile, dok su inercijalne sile svojevrsna analogija reakcijskih sila s obzirom da su reakcija na promjenu stanja gibanja. Informacija o izvoru koji stvara neko polje sila se prostorom širi brzinom svjetlosti. NAPOMENA: U biti, sve se sile mogu svesti na volumenske sile, s obzirom da su interakcije subatomskih čestica, atoma i molekula dominantno elektromagnetske prirode. Međutim, "pojednostavljenje" kontaktnom silom je dostatno, često i jedino prihvatljivo kod razmatranja konvencionalnih fizikalnih problema. Također treba napomenuti da je kod međudjelovanja čestica na molekularnoj razini (i niže) zapravo besmisleno govoriti o gravitacijskim i elektromagnetskim silama kao volumenskim silama, s obzirom da se elementarne mase i naboji mogu predstaviti točkama (nemaju volumena). Takve sile opravdavaju naziv "volumenska" tek na makrorazini. Vidi:
- Impuls sile Kategorija:Fizikalne veličine ko:힘 (물리학) simple:Force (physics)

Order of the Brethren of the Sword

The Livonian Brothers of the Sword (Latin Fratres militiae Christi, literally the "brothers of the army of Christ"), also known as the Christ Knights, Sword Brethren or The Militia of Christ of Livonia, was a military order organized in 1202 by Albert of Buxhoeveden, bishop of Riga (or Prince-Bishop of Livonia), and composed of German "warrior monks". Their rule was primarily based on that of the Knights Templar. From its foundation the Order tended to ignore its supposed vassalage to the bishops. In 1218 the bishop asked the Danish king, Valdemar II, for assistance — but Valdemar instead arranged a deal with the Brotherhood and conquered the north of Estonia. The Brotherhood's headquarters were at Viljandi (Fellin) in Estonia, where the walls of the master's castle are still standing. Other strongholds included Cesis (Wenden), Sigulda (Segewold) and Aizkraukle (Ascheraden). The commanders of Viljandi (Fellin), Kuldiga (Goldingen), Aluksne (Marienburg), Tallinn (Reval), and the bailiff of Paide (Weissenstein) belonged to the 5-member entourage of the Order's master. The Brothers were all but annihilated by the Lithuanians and Semigallians at the Battle of Šiauliai in 1236. In the following year, however, the Brotherhood was incorporated into the Order of Teutonic Knights. From that point on, they were in all respects (rule, clothing and policy) an autonomous branch of the Teutonic Order, headed by their own Master (who was de jure subject to the Order's Grand Master). Between 1237 and 1290 they conquered all of Courland, Livonia and Semigallia. In 1346 the Order bought the rest of Estonia from Valdemar IV Atterdag, King of Denmark. When the Teutonic Order fell into decline, following its defeat by the Poles at Tannenberg in 1410 and the secularization of its Prussian territories in 1525, the Livonian Knights managed to maintain an independent existence. Two years after the outbreak of the Livonian War, however, they suffered a decisive defeat by Russian troops in the Battle of Ergeme in 1560. The Livonian Order then sought protection from the Polish king Sigismund II Augustus, who already in 1557 had intervened in a war between the bishop of Riga and the Brothers. After coming to an agreement with the Polish king and his representatives (especially Mikołaj 'Czarny' Radziwiłł), the last Master, Gotthard Kettler, secularized the Order and converted to the Lutheran Church. In the southern part of the Brothers' lands he created the Duchy of Courland and Semigallia. Most of the remaining lands were seized by Poland-Lithuania. The north of Estonia was taken back by Denmark and Sweden.

Masters of the Livonian Order

- Wenno (von Rohrbach?) 1204–1209
- Volquin (von Naumburg?) 1209–1236

Masters of Livonia (within the Teutonic Order)

- Hermann Balk 1237–1238
- Dietrich von Grüningen 1238–1242
- Dietrich von Grüningen 1244–1246
- Andreas von Stierland 1248–1253
- Anno von Sangershausen 1253–1256
- Burchard von Hornhausen 1256–1260
- Werner von Breithausen 1261–1263
- Konrad von Mandern 1263–1266
- Otto von Lutterberg 1266–1270
- Walther von Nortecken 1270–1273
- Ernst von Rassburg 1273–1279
- Konrad von Feuchtwangen 1279–1281
- Wilken von Endorp 1281–1287
- Konrad von Herzogenstein 1288–1290
- Halt von Hohembach –1293
- Heinrich von Dinkelaghe 1295–1296
- Bruno 1296–1298
- Gottfried von Rogga 1298–1307
- Conrad von Jocke 1309–1322
- Johannes Ungenade 1322–1324
- Reimar Hane 1324–1328
- Everhard von Monheim 1328–1340
- Burchard von Dreileben 1340–1345
- Goswin von Hercke 1345–1359
- Arnold von Vietinghof 1359–1364
- Wilhelm von Vrymersheim 1364–1385
- R. von Eltz 1385–1389
- Wennemar Hasenkamp von Brüggeneye 1389–1401
- Konrad von Vietinghof 1401–1413
- Diderick Tork 1413–1415
- Siegfried Lander von Spanheim 1415–1424
- Zisse von Rutenberg 1424–1433
- Franco Kerskorff 1433–1435
- Heinrich von Bockenvorde 1435–1437
- H. Vinke von Overbergen 1438–1450
- Johann Osthoff von Mengede 1450–1469
- Johann Wolthuss von Herse 1470–1471
- Bernd von der Borch 1471–1483
- Johann Fridach von Loringhofe 1483–1494
- Wolter von Plettenberg 1494–1535
- Hermann Hasenkamp von Brüggeneye 1535–1549
- Johann von der Recke 1549–1551
- Heinrich von Galen 1551–1557
- Johann Wilhelm von Fürstenberg 1557–1559
- Godert (Gotthard) Kettler 1559–1561

External link