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Terminal velocity is the maximum speed attainable by an object as it falls through a fluid (air is the most common example). It is reached when the sum of the drag force ( F d ) and the buoyancy is equal to the downward force of gravity ( F G ) acting on the object.
Terminal velocity is achieved when the drag force is equal in magnitude but opposite in direction to the force propelling the object. Shown is a sphere in Stokes flow, at very low Reynolds number . Stokes flow (named after George Gabriel Stokes ), also named creeping flow or creeping motion , [ 1 ] is a type of fluid flow where advective ...
This velocity is the asymptotic limiting value of the acceleration process, because the effective forces on the body balance each other more and more closely as the terminal velocity is approached. In this example, a speed of 50 % of terminal velocity is reached after only about 3 seconds, while it takes 8 seconds to reach 90 %, 15 seconds to ...
For v i > v t, the velocity function is defined in terms of the hyperbolic cotangent function: = (+ ()). The hyperbolic cotangent also has a limit value of one, for large time t . Velocity asymptotically tends to the terminal velocity v t , strictly from above v t .
The azimuthal velocity component u φ does not depend on the stream function. Due to the axisymmetry, all three velocity components ( u ρ , u φ , u z ) only depend on ρ and z and not on the azimuth φ. The volume flux, through the surface bounded by a constant value ψ of the Stokes stream function, is equal to 2π ψ.
The terminal velocity depends on many factors including mass, drag coefficient, and relative surface area and will only be achieved if the fall is from sufficient altitude. A typical skydiver in a spread-eagle position will reach terminal velocity after about 12 seconds, during which time they will have fallen around 450 m (1,500 ft).
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If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube. Electronic sensing can be used for opaque fluids. Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes' law can be used to calculate the viscosity of the fluid. A ...