Calculating force on object being lowered/dropped into water

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Discussion Overview

The discussion focuses on calculating the hydrodynamic force on an object when it impacts the water surface at a constant velocity. It encompasses theoretical understanding and practical applications, with a particular interest in how this knowledge can be applied to design equations at different educational levels.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant seeks resources for understanding the hydrodynamic force on an object entering water.
  • Another participant suggests that the complexity of the topic may vary based on the educational level, mentioning buoyancy and surface tension for secondary school discussions.
  • A participant expresses a desire to understand the forces involved at a tertiary level to inform secondary school design equations, indicating familiarity with concepts like submerged buoyancy and drag.
  • There is a mention that calculating drag force and drag coefficient for a square object is complex, especially due to turbulent motion, and that experimental methods may be more practical.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to calculate the hydrodynamic force, and multiple views on the complexity and educational context of the topic remain present.

Contextual Notes

The discussion highlights the challenges in calculating hydrodynamic forces, particularly regarding turbulent motion and the need for experimental validation. There are also varying assumptions about the appropriate educational level for discussing these concepts.

PLI
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Any info/resources on calculating the hydrodynamic force on an object when it hits the water surface with constant velocity?

cheers
 
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Welcome to PF.
You mean something like this one or more general like this one?

Put another way - at what level should we be pitching this?
If just lowering an object into water, and at secondary school level, you'd only want to worry about bouyancy and, maybe, surface tension... for eg.
 
thanks simon,

both are good.
trying to get good understanding at "tertiary level", so that i can then put it into a design equation at "secondary school level" :)

haven't had a good read through either yet but I'm ok with submerged buoyancy, drag etc. it's the force acting on the object as it hits the water i need to understand better.

out of interest - do you have drag force and drag coefficient for a square object?
 
Not lying around no.
These things are not trivial to work out - especially as you'll get turbulent motion.
It's usually easier just to do an experiment.
 

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