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Mecanique

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Perpetual motion machines (hypothetical ) Understanding the chain fountain. Estimating the Airspeed Velocity of an Unladen Swallow. Hashing out the classic question with Strouhal numbers and simplified flight waveforms.

Estimating the Airspeed Velocity of an Unladen Swallow

After spending some time last month trying to develop alternate graphic presentations for kinematic ratios in winged flight, I decided to try to answer one of the timeless questions of science: just what is the airspeed velocity of an unladen swallow? What do you mean, an African or European Swallow? To begin with, I needed basic kinematic data on African and European swallow species. Although 47 of the 74 worldwide swallow species are found in Africa,1 only two species are named after the continent: the West African Swallow (Hirundo domicella) and the South African Swallow (Hirundo spilodera), also known as the South African Cave Swallow. Kinematic data for both African species was difficult to find, but the Barn or European Swallow (Hirundo rustica) has been studied intensively, and kinematic data for that species was readily available.

It’s a simple question of weight ratios Actually, wrong. References. Gravity Visualized.

Fluides

Throwing. Physique du motocross : comment contrôler son orientation en vol ? Dans de nombreux jeux vidéo de motocross, il est possible de faire pivoter la moto alors que l’on est en l’air.

Physique du motocross : comment contrôler son orientation en vol ?

Ce n’est pas une liberté que prennent les concepteurs du jeu avec la loi physique de conservation du moment cinétique. C’est en fait grace à cette même loi que les pilotes de motocross orientent leur moto alors qu’ils sont en l’air. Pour atterrir correctement, ils font tourner le cadre de leur engin en accélérant ou en freinant leur roue arrière. C’est aussi ainsi qu’ils conservent plus longtemps l’équilibre lors d’une roue avant. La video qui suit permet d’observer cette méthode grace à un ralenti remarquable (apres la 2ieme minute de la vidéo). Vidéo publié sur la chaine YouTube « SmarterEveryDay » Lorsque la moto est en l’air, elle ne subit de l’extérieur aucune action susceptible de mettre le cadre en rotation.

Le moment d’inertie de la roue et celui de la moto (plus précisément du système cadre + roue arrière bloquée), le moment cinétique total soit : . Complément. Cambridge gives Newton papers to the world. The Library holds the world’s largest and most significant collection of the scientific works of Isaac Newton (1642-1727), described by many as the greatest and most influential scientist who ever lived.

Cambridge gives Newton papers to the world

His works launch the new Cambridge Digital Library ( The project aims to make Cambridge a digital library for the world and will move on from Newton to some of the University Library’s other world-class collections in the realms of science and faith. These include the archive of the celebrated Board of Longitude and the papers of Charles Darwin. University Librarian Anne Jarvis said: “Over the course of six centuries Cambridge University Library's collections have grown from a few dozen volumes into one of the world's great libraries, with an extraordinary accumulation of books, maps, manuscripts and journals.

These cover every conceivable aspect of human endeavour, spanning most of the world's cultural traditions.” Hal.archives-ouvertes.fr/docs/00/12/93/93/PDF/ribeetal_text.pdf. Rspa.royalsocietypublishing.org/content/460/2051/3223.full.pdf. Viscosity. Etymology[edit] The word "viscosity" is derived from the Latin "viscum", meaning "anything sticky, birdlime made from mistletoe, mistletoe".

Viscosity

A viscous glue called birdlime was made from mistletoe berries and was used for lime-twigs to catch birds.[2] Definition[edit] Dynamic (shear) viscosity[edit] Laminar shear of fluid between two plates. In a general parallel flow (such as could occur in a straight pipe), the shear stress is proportional to the gradient of the velocity The dynamic (shear) viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. . The magnitude of this force is found to be proportional to the speed and the area of each plate, and inversely proportional to their separation The proportionality factor μ in this formula is the viscosity (specifically, the dynamic viscosity) of the fluid. The ratio where and is the local shear velocity. . , such as in fluid flowing through a pipe. SWEET MATH! (High Speed Honey Coiling) - Smarter Every Day 53. L'angle en V formé par les vagues de sillage d'un objet se déplaçant à la su.

Cours de mécanique des milieux continus.