# Yoyo

Topics: Aerodynamics, Fluid dynamics, Mach number Pages: 3 (927 words) Published: August 26, 2013
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a solid object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases. EARLY IDEAS

Humans have been harnessing aerodynamic forces for thousands of years with sailboats and windmills.[1] Images and stories of flight have appeared throughout recorded history,[2] such as the legendary story of Icarus and Daedalus.[3] Although observations of some aerodynamic effects such as wind resistance (e.g. drag) were recorded by Aristotle, Leonardo da Vinci and Galileo Galilei, very little effort was made to develop a rigorous quantitative theory of air flow prior to the 17th century. In 1505, Leonardo da Vinci wrote the Codex on the Flight of Birds, one of the earliest treatises on aerodynamics. He notes for the first time that the center of gravity of a flying bird does not coincide with its center of pressure, and he describes the construction of an ornithopter, with flapping wings similar to a bird's. Sir Isaac Newton was the first person to develop a theory of air resistance,[4] making him one of the first aerodynamicists. As part of that theory, Newton considered that drag was due to the dimensions of a body, the density of the fluid, and the velocity raised to the second power. These all turned out to be correct for low flow speeds. Newton also developed a law for the drag force on a flat plate inclined towards the direction of the fluid flow. Using F for the drag force, ρ for the density, S for the area of the flat plate, V for the flow velocity, andθ for the inclination angle, his law was expressed as  This equation is incorrect for the calculation of drag in most cases. Drag on a flat plate is closer to being linear with the angle of inclination as opposed to acting quadratically at...