كيلوجرام
(تم التحويل من كيلوغرام)
الكيلوجرام Kilogram، من وحدات القياس الأساسية في النظام الدولي، ويستخدم لقياس الكتلة، ويرمز له بالرمز (kg)، ويقابله الرطل في النظام الإنگليزي، اذ يساوي الرطل الواحد 0,4536 من كج. والكيلوجرام هو عبارة عن ألف (كيلو) من الجرامات.
| الكيلوجرام Kilogram | |
|---|---|
 الوزنة القياسية الدولية، مصنوعة من سبيكة بلاتينوم إريديوم، والمحفوظ في المكتب الدولي للأوزان والمعايير، تحت ظروف محددة بعد المؤتمر العام للأوزان والقياسات عام 1889.]] | |
| معلومات عامة | |
| نظام الوحدات | النظام الدولي |
| وحدة قياس | الكتلة |
| الرمز | kg |
| التحويلات | |
| 1 kg في ... | ... يساوي ... |
| U.S. customary | ≈ 2.205 الرطل |
| وحدات طبيعية | ≈ 4.59×107 Planck masses 1.356392608(60)×1050 hertz [Note 1] |
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التسمية والاستخدام
طبيعة الكتلة
The chains on the swing hold all the child’s weight. If one were to stand behind her at the bottom of the arc and try to stop her, one would be acting against her inertia, which arises purely from mass, not weight.
التاريخ
التعريفات المبكرة
النموذج الدولي للكيلوجرام
ثبات النموذج الدولي للكيلوجرام
Mass drift over time of national prototypes K21–K40, plus two of the IPK's sister copies: K32 and K8(41).[Note 2] All mass changes are relative to the IPK. The initial 1889 starting-value offsets relative to the IPK have been nulled.[1] The above are all relative measurements; no historical mass-measurement data is available to determine which of the prototypes has been most stable relative to an invariant of nature. There is the distinct possibility that all the prototypes gained mass over 100 years and that K21, K35, K40, and the IPK simply gained less than the others.
أهمية الكيلوجرام
تعريفات مستقبلية مقترحة
ثبات الواط
The NIST’s watt balance is a project of the U.S. Government to develop an “electronic kilogram.” The vacuum chamber dome, which lowers over the entire apparatus, is visible at top.
The local gravitational acceleration g is measured with exceptional precision with the help of a laser interferometer. The laser’s pattern of interference fringes—the dark and light bands above—blooms at an ever faster rate as a free-falling corner reflector drops inside an absolute gravimeter. The pattern’s frequency sweep is timed by an atomic clock.
أسلوب عد الذرات
كربون-12
مشروع أڤوگادرو
One of the master opticians at the Australian Centre for Precision Optics (ACPO) is holding a 1 kg, single-crystal silicon sphere for the Avogadro project. These spheres are among the roundest man-made objects in the world. If the best of these spheres were scaled to the size of earth, its high point—a continent-size area—would gently rise to a maximum elevation of only 2.4 meters above “sea level”.[Note 3]
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تراكم الأيون
قوة الأمبير
A magnet floating above a superconductor bathed in liquid nitrogen demonstrates perfect diamagnetic levitation via the Meissner effect. Experiments with an ampere-based definition of the kilogram flipped this arrangement upside-down: an electric field accelerated a superconducting test mass supported by fixed magnets.
تعدد وحدات النظام الدولي للقياس
المفردات
انظر أيضاً
الهوامش
- ^ One kilogram at rest has an equivalent energy approximately equal to the energy of photons whose frequencies sum to this value.
- ^ Prototype No. 8(41) was accidentally stamped with the number 41, but its accessories carry the proper number 8. Since there is no prototype marked 8, this prototype is referred to as 8(41).
- ^ The sphere shown in the photograph has an out-of-roundness value (peak to valley on the radius) of 50 nm. According to ACPO, they improved on that with an out-of-roundness of 35 nm. On the 93.6 mm diameter sphere, an out-of-roundness of 35 nm (undulations of ±17.5 nm) is a fractional roundness (∆r /r ) = 3.7×10−7. Scaled to the size of earth, this is equivalent to a maximum deviation from sea level of only 2.4 m. The roundness of that ACPO sphere is exceeded only by two of the four fused-quartz gyroscope rotors flown on Gravity Probe B, which were manufactured in the late 1990s and given their final figure at the W.W. Hansen Experimental Physics Lab at Stanford University. Particularly, “Gyro 4” is recorded in the Guinness database of world records (their database, not in their book) as the world’s roundest man-made object. According to a published report (221 kB PDF, here) and the GP‑B public affairs coordinator at Stanford University, of the four gyroscopes onboard the probe, Gyro 4 has a maximum surface undulation from a perfect sphere of 3.4 ±0.4 nm on the 38.1 mm diameter sphere, which is a ∆r /r = 1.8×10−7. Scaled to the size of earth, this is equivalent to an undulation the size of North America rising slowly up out of the sea (in molecular-layer terraces 11.9 cm high), reaching a maximum elevation of 1.14 ±0.13 m in Nebraska, and then gradually sloping back down to sea level on the other side of the continent.
المصادر
- ^ G. Girard (1994). "The Third Periodic Verification of National Prototypes of the Kilogram (1988–1992)". Metrologia. 31 (4): 317–336. Bibcode:1994Metro..31..317G. doi:10.1088/0026-1394/31/4/007.
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وصلات خارجية
 BIPM: The IPK in three nested bell jars | |
| NIST: K20, the US National Prototype Kilogram resting on an egg crate fluorescent light panel | |
| BIPM: Steam cleaning a 1 kg prototype before a mass comparison | |
| BIPM: The IPK and its six sister copies in their vault | |
| The Age: Silicon sphere for the Avogadro Project | |
| NPL: The NPL’s Watt Balance project | |
| NIST: This particular Rueprecht Balance, an Austrian-made precision balance, was used by the NIST from 1945 until 1960 | |
| BIPM: The FB‑2 flexure-strip balance, the BIPM’s modern precision balance featuring a standard deviation of one ten-billionth of a kilogram (0.1 µg) | |
| BIPM: Mettler HK1000 balance, featuring 1 µg resolution and a 4 kg maximum mass. Also used by NIST and Sandia National Laboratories’ Primary Standards Laboratory | |
| Micro-g LaCoste: FG‑5 absolute gravimeter, (diagram), used in national laboratories to measure gravity to 2 µGal accuracy |
- National Institute of Standards and Technology (NIST): NIST Improves Accuracy of ‘Watt Balance’ Method for Defining the Kilogram
- The UK’s National Physical Laboratory (NPL): Are any problems caused by having the kilogram defined in terms of a physical artefact? (FAQ - Mass & Density)
- NPL: Avogadro Project
- NPL: NPL watt balance
- Metrology in France: Watt balance
- Australian National Measurement Institute: Redefining the kilogram through the Avogadro constant
- International Bureau of Weights and Measures (BIPM): Home page
- NZZ Folio: What a kilogram really weighs
- NPL: What are the differences between mass, weight, force and load?
- BBC: Getting the measure of a kilogram
- NPR: This Kilogram Has A Weight-Loss Problem, an interview with National Institute of Standards and Technology physicist Richard Steiner
- Avogadro and molar Planck constants for the redefinition of the kilogram
- Realization of the awaited definition of the kilogram
Media related to Kilogram at Wikimedia Commons