Sergey Alexeyevich Chaplygin (; 5 April 1869 – 8 October 1942) was a Russian and

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

physicist,

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

, and mechanical

engineer Engineers, as practitioners of engineering, are professionals who Invention, invent, design, build, maintain and test machines, complex systems, structures, gadgets and materials. They aim to fulfill functional objectives and requirements while ...

. He is known for mathematical formulas such as Chaplygin's equation and for a hypothetical substance in

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

called Chaplygin gas, named after him. He graduated in 1890 from Moscow University, and later became a professor. He taught mechanical engineering at Moscow Higher Courses for Women in 1901, and of applied mathematics at Moscow School of Technology, 1903. He was appointed Director of the courses in 1905. Leonid I. Sedov was one of his students. Chaplygin's theories were greatly inspired by N. Ye. Zhukovsky, who founded the Central Institute of Aerodynamics. His early research focused on hydromechanics. His "Collected Works", consisting of 4 volumes, were published in 1948.

Biography

Early life

Chaplygin was born to Aleksei Timofeevich Chaplygin, a shop assistant, and Anna Petrovna in Ranenburg (present day Chaplygin), Russia. After his father died when he was 2 years old, his mother remarried a tradesman and they moved to Voronezh. There, he attended the Voronezh Gymnasium, which he graduated in 1886. Soon after, he attended the Moscow University, specializing in Physics and Mathematics, which he graduated from in 1890. There he met and was strongly influenced by Nikolai Egorovich Zhukovsky. In 1893, he published his first work, ''On certain cases of the motion of a solid body in a fluid'', for which he received the N. D. Brashman Award. After graduating from the university, he went on to become a professor there. In 1897, he published ''On the motion of a heavy body of revolution in a horizontal plane,'' which was the first to present the general equation of motion of a nonholonomic system. This equation is a generalisation of Lagrange's equation. In 1899, he was awarded the Gold Medal of the St. Petersburg Academy of Sciences.

Death

Chaplygin died of a brain haemorrhage in October 1942.

Honours and awards

* Hero of Socialist Labour (February 1, 1941) * Two Orders of Lenin (February 1, 1941 and December 22, 1933) * Order of the Red Banner of Labour, twice (July 10, 1927 and ?) * Zhukovsky Prize (1925) * N. D. Brashman Prize (1897) Chaplygin was elected to the Russian Academy of Sciences (the Academy of Sciences of the USSR in 1925-1991) in 1924. The lunar crater Chaplygin and town Chaplygin are named in his honour.

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