Kilogram
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Kilogram (lambangna kg) nyaéta unit dasar SI pikeun massa. Sa-gram diwatesan ku sapersaréwu kilogram. Konversi unit ngagambarkeun unit ékivalén massa dina sistim séjén.
Tikelan édit
Émbohan SI dipaké pikeun méré ngaran tikelan atawa babagian tina kilogram. Nu ilahar dipaké nyaéta,
- ton = 1 000 kg (kuduna mah disebutna mégagram, ngan jarang pisan dipaké) (kadé pahili jeung US short ton, 2000 pon atawa kira 907 kg)
- gram = 1/1 000 kg
- milligram = sapersaréwu gram = sapersayuta kilogram
- mikrogram = sapersayuta gram = 1/(10^9) kg
Watesan édit
Kilogram mangrupa hiji-hijina unit SI nu masih kénéh watesanana dihubungkeun jeung artéfak batan sipat fisik.
Kilogram pituinna diwatesan salaku massa saléter cimurni dina temperatur 4 darajat Celsius jeung tekenan atmosfir baku. Watesan ieu hésé pisan diwujudkeun sacara akurat, salah sahijina sabab dénsitas cai gumantung kana tekenan, sedengkeun unit tekenan ngawengku massa salaku salah sahiji faktorna, antukna ngagasilkeun kagumantungan sirkular dina watesan kilogram.
Pikeun nyingkahan masalah ieu, watesan kilogram dibaru deui sacara tepat massa hiji baku husus nu dijieun sasarua-saruana jeung watesan asalna. Saprak 1889, sistim SI ngawatesan unit ieu sarua jeung massa prototipe kilogram internasional, nu dijieun tina watang alloy platinum jeung iridium nu panjang jeung diaméterna 39 mm, sarta diteundeun di Biro Internasional Timbangan jeung Ukuran. Salinan resmi prototipe kilogram dijieun pikeun prototipe nasional, nu dibandingkeun jeung prototipe Paris ("Le Grand Kilo"), kasarna unggal 10 taun. Prototipe kilogram internasional dijieun taun 1880-an.
Dumasar watesan, kasalahan dina kabisaulangan watesan kiwari téh enol; ngan, dina harti ilahar kecapna, aya dina rentang 2 mikrogram. Ieu bisa kapanggih mun urang ngabandingkeun baku jeung salinan resmina, nu dijieun tina bahan sarta diteundeun dina kaayaan nu sarua. euweuh nu bisa mastikeun mana nu leuwih stabil, naha nu asli aatawa nu salinanana. Ku kituna, prosedur ieu dipigawé unggal opat puluh taun.
Prototipe internasional kilogram sigana ngahampangan kira 50 mikrogram salila saabad ieu, ku sabab nu tacan kanyahoan (dilaporkeun dina Der Spiegel, 2003 #26). Bébédaan nu kapanggih dina prototipena nyedek kana perluna néangan watesan anyar kilogram. Najan bener mun disebut yén sadaya objék di mayapada nambahan massana 50 mikrogram per kilogramna, sawangan ieu patojaiyah jeung ngéléhkeun tujuan unit baku massa.
Watesan ka hareup nu diajengkeun édit
Aya sawatara usaha pikeun ngawanohkeun hiji watesan tina jalan fundaméntal atawa konstanta atomik:
Atom-counting approaches édit
- The Watt balance uses the current balance that formerly was used to define the ampere to relate the kilogram to a value for Planck's constant, based on the definitions of the volt and the ohm.
- The Avogadro approach attempts at defining the kilogram by a fixed count of silicon atoms. As a practical réalization, a sphere will be used where the size is méasured by interferometry.
- The ion accumulation approach involves accumulation of gold atoms and méasuring the electrical current required to neutralise them.
Fundamental-constant approaches édit
- The levitated superconductor approach relates the kilogram to electrical quantities by levitating a superconducting body in a magnetic field generated by a superconducting coil, and méasuring the electrical current required in the coil.
- Since the values of the Josephson (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values, it is possible to combine these values (KJ ≡ 4.835 979×1014 Hz/V and RK ≡ 2.581 280 7×104 Ω) with the definition of the ampere to define the kilogram. As follows:
- The kilogram is the mass which would be accelerated at precisely 2×10-7 m/s² if subjected to the per metre force between two straight parallel conductors of infinite length, of negligible circular cross section, placed 1 metre apart in vacuum, through which flow a constant current of exactly 6.241 509 629 152 65 × 1018 elementary charges per second.
Patalina jeung beurat édit
Nalika sipat hiji barang disebutkeun dina kilogram, sipat ieu nujul ampir salawasna ka massa, padahal sipat dina pamakéan sapopoé mindengna disebut "beurat", a usage much deprecated by those communities (physicists and engineers) that prefer weight always to méan "gravitational force". Occasionally the gravitational force on an object is given in "kilograms", but the unit used is not a true kilogram: it is the deprecated kilogram-force (kgf), also known as the kilopond (kp). An object of mass 1 kg at the surface of the Earth will be subjected to a gravitational force (that is to say, it will have a weight) of approximately:
- 1 kgf = 1 kg × 9,806 65 m/s² = 9.806 65 N
nu mana N salaku Newton, unit gaya SI. Catet yén faktor 9,806 65 ngan disatujuan salaku rataan (CGPM ka-3 (1901), CR 70), salaku niléy tepat g, laju gravitasi lokal, béda-béda gumantung luhur-handap sarta tempatna di Bumi. (Tempo graviti baku).