How can i calculate the speed of an object in water

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Discussion Overview

The discussion centers around calculating the speed of an object moving through sea water, specifically focusing on the terminal velocity of a 100-tonne streamlined steel object. Participants explore methods for calculating this speed and the factors that influence it, including gravity, buoyancy, and drag forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to understand how to calculate the speed of a 100-tonne steel object falling through sea water and asks for a general method applicable to any object.
  • Another participant suggests that a rough approximation can be made by comparing gravity and buoyancy forces to determine acceleration, while noting that drag forces must be considered for more accuracy.
  • A third participant provides links to wiki articles on terminal velocity and drag coefficient as resources for further understanding.
  • A participant shares their understanding of the terminal velocity equation and questions its accuracy, expressing concern about obtaining a high speed of 65 meters per second with certain materials and suggesting that a drag coefficient of 1 may yield more realistic figures.

Areas of Agreement / Disagreement

Participants express differing views on the accuracy of the terminal velocity equation and the appropriate values for drag coefficients, indicating that the discussion remains unresolved regarding the best approach to calculate speed in water.

Contextual Notes

Participants mention various factors that may influence the calculations, such as the density of the fluid and the projected area of the object, but do not reach a consensus on the completeness or accuracy of the equation used.

DouglasEdward
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I would like to know how fast an object will move through sea water.
Do you know if an accurate figure can be calculated? if so how?
I would like to know how fast 100 tonnes of steel -(streamlined )would fall through sea water.
I would also like to how how to calculate the figure for any object.
 
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For a rough approximation you can just calculate gravity vs. buoyancy forces to determine the acceleration.

For a more accurate calculation you will need to take into account drag forces.
 
thanks for your replies,


where
Vt = terminal velocity,
m = mass of the falling object,
g = acceleration due to gravity,
Cd = drag coefficient,
ρ = density of the fluid through which the object is falling, and
A = projected area of the object.

i just want to chack i understnad the equation...

( 2xmass x accelaration gravity) divided by (density x area x drag coefficient)
= X square root of x = Vt

how accurate is this euquation considered to be; what is still missing.?

I put some very dense materials in with very low drag coefficients and i got figure up to 65 metre per second which seems a little fast

i got other things in and think that the figure is more realistic by making the drag coefficient 1 rather than 0.09.
 

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