Guillaume Amontons was a French scientific instrument inventor and
physicistA physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
. He was one of the pioneers in
tribologyTribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear...
, apart from
Leonardo da VinciLeonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...
,
John Theophilus DesaguliersJohn Theophilus Desaguliers was a natural philosopher born in France. He was a member of the Royal Society of London beginning 29 July 1714. He was presented with the Royal Society's highest honour, the Copley Medal, in 1734, 1736 and 1741, with the 1741 award being for his discovery of the...
, Leonard Euler and
Charles-Augustin de CoulombCharles-Augustin de Coulomb was a French physicist. He is best known for developing Coulomb's law, the definition of the electrostatic force of attraction and repulsion. The [SI unit] of charge, the coulomb, was named after him....
.
Life
Guillaume was born in Paris, France. His father was a
lawyerA lawyer, according to Black's Law Dictionary, is "a person learned in the law; as an attorney, counsel or solicitor; a person who is practicing law." Law is the system of rules of conduct established by the sovereign government of a society to correct wrongs, maintain the stability of political...
from
NormandyNormandy is a geographical region corresponding to the former Duchy of Normandy. It is in France.The continental territory covers 30,627 km² and forms the preponderant part of Normandy and roughly 5% of the territory of France. It is divided for administrative purposes into two régions:...
who had moved to the French capital. While still young, Guillaume lost his hearing, which may have motivated him to focus entirely on science. He never attended a
universityA university is an institution of higher education and research, which grants academic degrees in a variety of subjects. A university is an organisation that provides both undergraduate education and postgraduate education...
, but was able to study
mathematicsMathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
, the physical sciences, and
celestial mechanicsCelestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...
. He also spent time studying the skills of
drawingDrawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, markers, styluses, and various metals .An artist who...
,
surveyingSee Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...
, and
architectureArchitecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...
.
He died in
ParisParis is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
,
FranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
.
Work
He was supported in his research career by the
governmentGovernment refers to the legislators, administrators, and arbitrators in the administrative bureaucracy who control a state at a given time, and to the system of government by which they are organized...
, and was employed in various
public worksPublic works are a broad category of projects, financed and constructed by the government, for recreational, employment, and health and safety uses in the greater community...
projects.
Scientific instruments
Among his contributions to scientific instrumentation were improvements to the
barometerA barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...
(1695),
hygrometerA hygrometer is an instrument used for measuring the moisture content in the environmental air, or humidity. Most measurement devices usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed...
(1687), and
thermometerDeveloped during the 16th and 17th centuries, a thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor Developed during the 16th and 17th centuries, a thermometer (from the...
(1695), particularly for use of these instruments at sea. He also demonstrated an optical telegraph and proposed the use of his clepsydra (
water clockA water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into or out from a vessel where the amount is then measured.Water clocks, along with sundials, are likely to be the oldest time-measuring instruments, with the only exceptions...
) for
keeping time on a ship at seaA marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
.
Thermodynamics
Amontons investigated the relationship between
pressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
and
temperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
in
gasGas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
es though he lacked
accurate and preciseIn the fields of science, engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which...
thermometerDeveloped during the 16th and 17th centuries, a thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor Developed during the 16th and 17th centuries, a thermometer (from the...
s. Though his results were at best semi-
quantitativeIn the social sciences, quantitative research refers to the systematic empirical investigation of social phenomena via statistical, mathematical or computational techniques. The objective of quantitative research is to develop and employ mathematical models, theories and/or hypotheses pertaining to...
, he established that the pressure of a gas increases by roughly one-third between the temperatures of
cold and the
boiling pointThe boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
of
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. This was a substantial step towards the subsequent
gas lawsThe early gas laws were developed at the end of the 18th century, when scientists began to realize that relationships between the pressure, volume and temperature of a sample of gas could be obtained which would hold for all gases...
and, in particular,
Charles's lawCharles' law is an experimental gas law which describes how gases tend to expand when heated. It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles...
.
His work led him to speculate that a sufficient reduction in temperature would lead to the disappearance of pressure. Thus, he is the first researcher to discuss the concept of an
absolute zeroAbsolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....
of temperature, a concept later extended and rationalised by
William Thomson, 1st Baron KelvinWilliam Thomson, 1st Baron Kelvin OM, GCVO, PC, PRS, PRSE, was a mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging...
.
Friction
In 1699, Amontons published his rediscovery of the laws of
frictionFriction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
first put forward by
Leonardo da VinciLeonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...
. Though they were received with some scepticism, the laws were verified by
Charles-Augustin de CoulombCharles-Augustin de Coulomb was a French physicist. He is best known for developing Coulomb's law, the definition of the electrostatic force of attraction and repulsion. The [SI unit] of charge, the coulomb, was named after him....
in 1781.
Amontons' Laws of Friction
Amontons' Laws of Friction, first explored by Leonardo da Vinci but never published, were rediscovered and first recorded in print during the late 17th century.
There 3 laws of friction are:
- 1. The force of friction is directly proportional to the applied load. (Amontons 1st Law)
- 2. The force of friction is independent of the apparent area of contact. (Amontons 2nd Law)
- 3. Kinetic friction is independent of the sliding velocity. (Coulomb's Law)
NOTE: These 3 laws only apply to dry
frictionFriction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
, in which the addition of a
lubricantA lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
modifies the tribological properties signifiantly.
Explaining Friction
By looking at any surface on the microscopic level, one would find that it is never perfectly flat. There would exist many tiny bumps and craters, due to imperfections on the surface and the alignment of molecules. (The skin does not feel the bumps and craters because they are too small to be detected.)
Considering a smooth stone on a smooth flat road, the two surfaces would be still in contact, but only at a few points (the bumps do not fit exactly into the craters). Due to electrostatic forces of repulsion between the atoms(nuclei against nuclei and electrons against electrons) of the stone and the road, the road will exert a force on the stone, and the stone will exert a force on the road (normal contact forces). The force exerted on the stone would be the NORMAL contact force.
If an external force cause the stone to move to the RIGHT, the forces that the road exert on the stone would be slightly skewed to the LEFT, thus the net force from the road on the stone will be pointing UP but LEFTWARD from the sum of all of the electrostatic forces(tilted contact force). As the vertical component of the net force is the normal contact force, the extra horizontal leftward component of the force would therefore be the FRICTIONAL force.
(Note: friction force OPPOSES sliding of two surfaces in contact. On a macro level you could not walk forward without friction pushing you forward)
Amontons First Law Explained
Suppose the stone had a greater mass (hence greater weight as g=constant). The stone would then:
- exert a greater force on the road (the increased load causes the separation distance of the nuclei to decrease, force of repulsion becomes stronger(inverse-square law
In physics, an inverse-square law is any physical law stating that a specified physical quantity or strength is inversely proportional to the square of the distance from the source of that physical quantity....
) ), AND
- more of the atoms of the road and the stone would be in contact.
Hence, when the stone is moved, a greater frictional force would be produced (more areas of contact means that more forces can be skewed, producing more horizontal components of the contact forces).
Amontons law applies to any 2 surfaces, regardless of their orientation. (e.g. pressing a brick against the ceiling, etc.)
NOTE: Applied load means the
normal contact force acting on the stone. That is, if the stone is being pushed down harder while it was trying to move, the force acting on the ground increases, and hence the force of the ground acting on the stone (normal contact) increases. This means that more force is required to move the stone across the ground. (frictional force increase)
Amontons Second Law Explained
What this law means is that if two
equal masses made of
similar material are resting on the
same surface with
different areas of contact, they would require the
same amount of force to start moving (overcome static friction) and to move at constant speed.
To put it in another way: considering 2 equal masses, and the area in contact in situation A is greater than in situation B. This only means that in situation A, the load is distributed across a greater area then in situation B. However, the
applied load is still the same! Thus to move both masses, we would require the same amount of applied force to overcome friction. (Amontons First Law)
In summary
,
where μ is the coefficient of friction and N is the normal contact force.
This is as predicted by Amontons' two laws, where F
fric depends only on the normal contact force (reaction pair of the applied load), and is independent of the surface area in contact.
However, exceptions to Amontons' Law have been observed in various nanometric scenarios. For example, when two surfaces get close enough such that molecular interactions and atomic forces come into play, the two surfaces are attracted together and form what was known as 'negative load'.
Honours
- Member, Académie des Sciences, (1690)
- The crater Amontons
Amontons is a tiny lunar crater in the western half of the Mare Fecunditatis. It is a circular, cup-shaped formation that has been excavated out of the level surface by the impact, and is the same dark hue as the surrounding mare. When the sun is at a low angle, multiple ghost-craters are visible...
on the MoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
is named after him.
Further reading
- Asimov's Biographical Encyclopedia of Science and Technology, Isaac Asimov
Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...
, Doubleday & Co., Inc., 1972The year 1972 in literature involved some significant events and new books.-Fiction:*Richard Adams - Watership Down*Jorge Amado - Teresa Batista Cansada da Guerra *Martin Amis - The Rachel Papers...
, ISBN 0-385-17771-2., pp18-19
External links
- The Galileo Project entry on which this biography is partly based.
- Short biography, NNDB
The Notable Names Database , produced by Soylent Communications, the same entity that produces Rotten, Daily Rotten, Dr. Sputnik's Society Pages and Penny Postcards, is an online database of biographical details of over 36,000 people of note...
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