General information
Mass is the property of physical bodies to resist acceleration. Mass, unlike weight, does not change depending on the environment and does not depend on the gravitational force of the planet on which this body is located. Mass m
determined using Newton's second law, according to the formula:
F
=
m a
, where
F
is force and
a
is acceleration.
Mass and weight
The word “weight” is often used in everyday life when people talk about mass. In physics, weight, in contrast to mass, is a force acting on a body due to the attraction between bodies and planets. Weight can also be calculated using Newton's second law: P
=
m g
, where
m
is the mass and
g
is the acceleration due to gravity. This acceleration occurs due to the gravitational force of the planet near which the body is located, and its magnitude also depends on this force. The acceleration of free fall on Earth is 9.80665 meters per second, and on the Moon it is approximately six times less - 1.63 meters per second. Thus, a body weighing one kilogram weighs 9.8 newtons on Earth and 1.63 newtons on the Moon.
Moon mass 7.3477×10²² kg
Gravitational mass
Gravitational mass shows what gravitational force acts on a body (passive mass) and with what gravitational force the body acts on other bodies (active mass). With an increase in active gravitational mass
body, its force of attraction also increases. It is this force that controls the movement and location of stars, planets and other astronomical objects in the universe. Tides are also caused by the gravitational forces of the Earth and Moon.
With increasing passive gravitational mass
the force with which the gravitational fields of other bodies act on this body also increases.
Inert mass
Inertial mass is the property of a body to resist movement. It is precisely because a body has mass that a certain force must be applied to move the body from its place or change the direction or speed of its movement. The greater the inertial mass, the greater the force required to achieve this. Mass in Newton's second law is precisely inertial mass. The gravitational and inertial masses are equal in magnitude.
Mass and relativity
According to the theory of relativity, gravitating mass changes the curvature of the space-time continuum. The greater the mass of a body, the stronger the curvature around this body, therefore, near bodies of large mass, such as stars, the trajectory of light rays is bent. This effect in astronomy is called gravitational lenses. On the contrary, far from large astronomical objects (massive stars or their clusters called galaxies), the movement of light rays is linear. The main postulate of the theory of relativity is the postulate about the finiteness of the speed of propagation of light. Several interesting consequences follow from this. Firstly, one can imagine the existence of objects with such a large mass that the second cosmic velocity of such a body will be equal to the speed of light, i.e. no information from this object will be able to reach the outside world. Such cosmic objects in the general theory of relativity are called “black holes” and their existence has been experimentally proven by scientists. Secondly, when an object moves at near-light speed, its inertial mass increases so much that local time inside the object slows down compared to time. measured by stationary clocks on Earth. This paradox is known as the “twin paradox”: one of them goes into space flight at near-light speed, the other remains on Earth. Upon returning from the flight twenty years later, it turns out that the twin astronaut is biologically younger than his brother!
Units
Kilogram
In the SI system, mass is expressed in kilograms. The kilogram is determined based on the exact numerical value of Planck's constant h
, equal to 6.62607015×10⁻³⁴, expressed in J s, which is equal to kg m² s⁻¹, with the second and meter being determined by the exact values of
c
and Δ
ν
Cs. The mass of one liter of water can be approximately considered equal to one kilogram. The derivatives of kilogram, gram (1/1000 of a kilogram) and ton (1000 kilograms) are not SI units, but are widely used.
Electron-volt
Electronvolt is a unit for measuring energy. It is usually used in the theory of relativity, and energy is calculated using the formula E
=
mc²
, where
E
is energy,
m
is mass, and
c
is the speed of light.
According to the principle of equivalence of mass and energy, an electronvolt is also a unit of mass in the system of natural units, where c
is equal to one, which means mass equals energy. Electrovolts are mainly used in nuclear and atomic physics.
Atomic mass unit
Atomic mass unit ( a.u.m.
) is intended for masses of molecules, atoms, and other particles. One a. e.m. is equal to 1/12 the mass of a carbon nuclide atom, ¹²C. This is approximately 1.66 × 10 ⁻²⁷ kilograms.
Slug
Slugs are used primarily in the British Imperial system in Great Britain and some other countries. One slug is equal to the mass of a body that moves with an acceleration of one foot per second per second when a force of one pound-force is applied to it. This is approximately 14.59 kilograms.
The mass of the Sun is 1.9884×1030 kg
Solar mass
Solar mass is a measure of mass used in astronomy to measure stars, planets and galaxies. One solar mass is equal to the mass of the Sun, that is, 2 × 10³⁰ kilograms. The mass of the Earth is approximately 333,000 times less.
Carat
Carats measure the weight of precious stones and metals in jewelry. One carat is equal to 200 milligrams. The name and the size itself are associated with the seeds of the carob tree (in English: carob, pronounced “carob”). One carat used to be equal to the weight of the seed of this tree, and buyers carried their seeds with them to check whether they were being deceived by sellers of precious metals and stones. The weight of a gold coin in Ancient Rome was equal to 24 carob seeds, and therefore carats began to be used to indicate the amount of gold in the alloy. 24 karat is pure gold, 12 karat is half gold alloy, and so on.
Soft metric weight labeling on food products in Canada
Grand
The grain was used as a measure of weight in many countries before the Renaissance. It was based on the weight of grains, mainly barley, and other popular crops at the time. One grain is equal to about 65 milligrams. This is a little more than a quarter of a carat. Until carats became widespread, grains were used in jewelry. This measure of weight is still used to this day to measure the mass of gunpowder, bullets, arrows, and gold foil in dentistry.
Other units of mass
In countries where the metric system is not adopted, the British Imperial system is used. For example, in the UK, USA and Canada, pounds, stones and ounces are widely used. One pound is equal to 453.6 grams. Stones are used mainly only to measure human body weight. One stone is approximately 6.35 kilograms or exactly 14 pounds. Ounces are primarily used in cooking recipes, especially for foods in small portions. One ounce is 1/16 of a pound, or approximately 28.35 grams. In Canada, which formally adopted the metric system in the 1970s, many products are sold in rounded imperial units, such as one pound or 14 fluid ounces, but are labeled with weight or volume in metric units. In English, such a system is called “soft metric ”
), in contrast to the “hard metric” system (English
hard metric
), in which the rounded weight in metric units is indicated on the packaging. This image shows "soft metric" food packaging with weight in metric units only and volume in both metric and imperial units.
Bibliography
Author of the article: Kateryna Yuri
What is an ounce of gold and how many grams is it?
The first ounce appeared in Ancient Rome. It was a coin made of an alloy of tin, copper and lead. The obverse of the sign depicted the profile of Roma, the founder and first king of the state. A Roman ounce weighed 27.28 grams. This value began to be taken as a measure of mass. It was adopted in different countries, but slightly transformed.
So, in the USA, weight is calculated relative to the avoirdupois pound, 1/16 of it is an ounce, that is, 28.35 grams. There is also a fluid ounce. For example, it is used in the UK, measured in cubic centimeters. One unit of volume is equal to 28.41 (one cup of expresso). The troy ounce is used to weigh and evaluate precious metals. Let's talk about her.
A troy ounce of gold is
An ounce of gold , silver, and platinum is 9.7% heavier than the same ounce of avoirdupois. It is not used for weighing metals at stock exchanges, banks, or in the jewelry industry. However, on the Internet, due to confusion in concepts, they can sell jewelry by indicating the weight in ounces, but not indicating which ones. It’s worth clarifying, otherwise you can overpay by the same 9.7%.
An ounce of gold in grams is equal to 31.104. It is calculated relative to the troy pound, of which it is 1/12. The abbreviation “t oz” has been approved for the measurement unit. Let's assume the option ozt. Among modern troy ounces of gold in grams, the most massive. In the old days, it was equal to the apothecary weight measure among the British. Medicines, herbs and potions were packaged in just 31.104 grams.
The Troy pound also fell out of use. Only avoirdupois remains in use in Great Britain. But the troy ounce has been preserved as a measure of weight for precious metals.
History of the troy ounce of gold
Historians believe that the name of the measure of weight is not associated with the ancient Greek city of Troy. The name of the ounce, scientists note, was formed in Troyes Champagne. This is a province of France, where a fair was organized back in the 5th century. By the 14th century it had become the largest in Europe and one of the main centers of world trade.
People came to the market from all over the world, and confusion arose in the weight measures, because they differed among residents of different countries. Even in France itself at that time there was a Toulouse pound, a Cologne pound and several more - each city had its own. Troyes also had its own troy pound.
The first mention of it dates back to 1390. The data is provided by the Oxford Dictionary. Market traders made the local weight measure uniform for the fair. Everyone is accustomed to measuring goods in troy ounces. Many lands adopted the French measure, including England.
The troy ounce had a fixed weight, which was convenient. For comparison, in Europe there was such a measure as gran. This is the average weight of barley grain. What kind of grain should be considered average and what exactly its mass is, people have been arguing for centuries.
The cost of an ounce of gold in 2014-2015
A gold ounce today is worth the same as in January 2014. The indicator recently returned to its position. Almost the entire last year, the precious metal lost in price, only in the fall it began to regain lost ground and, ultimately, reaching $1,200 for 31,104 grams.
A sharp jump in the value of gold has been recorded on the ruble market. The phenomenon is associated with the devaluation of the Russian currency, its fall against the euro and dollar. At the beginning of 2014, they were asking about 1,300 rubles per gram. Now more than 2000 rubles are paid. The increase was over 70%. Experts are inclined to believe that the devaluation of the ruble will continue in 2015, which means that gold prices are also predicted to rise further.
In addition to data on how many grams are in an ounce of gold , there is information about the cost of 1 unit of weight of valuable elements since 1950. So, then for 31.104 grams of yellow metal they asked for 34.7 dollars. A sharp jump occurred in 1973.
From 97 conventional units the price increased to 160 dollars. From 1979 to 80, the cost increased by 300 bucks and began to fall from 600 to 299 dollars. A new round of growth began in 2002. For 13 years now, they have been asking for more and more per ounce of gold.
Variations in the cost of an ounce of gold, taking into account markups
1 ounce of gold has a fixed price on exchanges, in bullion. But in jewelry stores, for example, bank settings are only a starting point. A markup is made for the work of jewelers, the costs of maintaining retail outlets, and the costs of paying sellers are taken into account. As a result, the cost of an ounce of gold today may differ greatly from its actual value.
This, by the way, is associated with a drop in demand for investment coins of the Central Bank of Russia. The following people understand that 18,300 rubles for a sample weighing 7.78 grams is an inflated price. Therefore, throughout 2014, investments were made in European coins, such as the Philharmonic and the American Eagle. The latter contains exactly one troy ounce. The price from gold , because the sign is platinum.
Although the Central Bank miscalculated its sales policy, it continued to purchase the precious metal itself. The organization's storerooms contained 33,300,000 ounces of gold. The price of inventories has increased with their quantity. In February 2015, the Central Bank increased reserves to 37,000,000 troy ounces.
On bullion coins the content of troy ounces is written. However, this does not mean that the coin weighs exactly the same. Platinum "Eagle" is made of pure metal. But the Krugerrand is cast from a 22-carat alloy, which contains only 91.677% of the precious element. It turns out that the coin contains an ounce of gold , but the price today is calculated taking into account the alloy - the addition of silver, copper and more.
