What is the max speed an object can sink in water?

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Like terminal velocity of an object falling in the air, is there the same said type terminal velocity for objects sinking in water? If so, how deep would an object have to be sinking in order to reach the speed? Does the weight of the object in water affect the speed as well?

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13 Answers

Anonymous 0 Comments

The simplest approach would be using Stokes law for settling velocity. This equation will tell you how fast a sphere with a certain radius and density will sink in a fluid which has it’s own density and viscosity.

V=2/9(gr2)(d1-d2)/µ

where
V = velocity of fall (cm/sec)
g = acceleration of gravity (cm/sec2)
r = “equivalent” radius of particle
d1 = density of particle (g/cm3)
d2 = density of medium (g/cm3)
µ = viscosity of medium (g/cm-sec)

Anonymous 0 Comments

No simple answer here. Make it heavier and more streamlined and it’ll sink faster. A smooth tungsten rod with fins would have a frighteningly high terminal velocity even in water. But any given object will approach a terminal velocity in water the same way it does in air.

Anonymous 0 Comments

If you’ve ever been in the water you might have noticed that things tend to fall much slower than in air. But more weirdly is that they don’t seem to speed up! This is because the terminal velocity of objects in water is typically reached rather quickly.

For the second part of your question the weight of an object doesn’t matter as much as its density. A rock will fall but a battleship will float. In a way you might think of objects that float in water as having a negative terminal velocity, they want to rise.