Terminal Velocity
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Given the density and volume of a spherical object, the TERMINAL VELOCITY of that object, released from rest (initial velocity = 0) in water or other viscous fluid can be calculated based on the condition that, at terminal velocity, the total drag force (velocity-dependent) plus buoyant force will equal and therefore cancel the gravitational force acting on the object. This assumes a purely Stokes (non-turbulent) flow around a smooth sphere, with drag being defined as = 1/2 • p • v^2 • A • Cd where:
p = the density of the fluid (1000Kg/m^3 for water, 1025Kg/m^3 for seawater)
v = velocity (setting Fg = Fb + Fd and solving for v yields terminal velocity)
A = the cross-sectional Area impinged by the flow (= pi • r^2 for a Sphere)
Cd = the Coefficient of Drag which is 0.47 for a smooth sphere
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