Sinking Boat: Calculations & Results

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    Boat Calculations
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Homework Help Overview

The discussion revolves around a physics problem involving a sinking boat with specific dimensions and a hole in its bottom. Participants explore the implications of water entering the boat through the hole and the resulting effects on buoyancy and water levels inside and outside the boat.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants attempt to calculate the velocity of water entering through the hole and the time it takes for the boat to sink. They also discuss the relationship between the water levels inside and outside the boat and question the assumptions made regarding buoyancy and hydrostatic pressure.

Discussion Status

The discussion is ongoing, with participants providing various calculations and questioning each other's reasoning. Some participants express uncertainty about their calculations, while others suggest reconsidering certain assumptions, particularly regarding the hydrostatic pressure and the implications of water levels on buoyancy.

Contextual Notes

There are constraints regarding the initial conditions of the boat, including its dimensions and the height of water above the hole. Participants also note the need to clarify the definitions of variables used in their calculations, particularly in relation to buoyancy and the mass of the water inside the boat.

  • #61
I don't see how a pressure notably below ambient downstream pressure could be maintained in the stream. Such a pressure difference sucks in water from the outside. That is happening, of course, but I would expect that to form a somewhat stable vortex without large pressure differences.
 
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  • #62
mfb said:
I don't see how a pressure notably below ambient downstream pressure could be maintained in the stream. Such a pressure difference sucks in water from the outside. That is happening, of course, but I would expect that to form a somewhat stable vortex without large pressure differences.
I had trouble finding anything on this that is not behind a paywall. Finally found https://books.google.com.au/books?i...zAG#v=onepage&q=flow submerged sluice&f=false. See eqn 5.24
 
  • #63
I cannot access the previous page in the preview, which makes the formula unclear.
 
  • #64
mfb said:
I cannot access the previous page in the preview, which makes the formula unclear.
It has a diagram with H1 as the depth in front of the sluice, H2 as the general depth downstream of the sluice, and H3 as the depth just after the sluice. The surface water is lower just after the sluice than further downstream, so H3 < H2, as per the formula. The height difference used for the flow rate is H1-H3.
 
  • #65
Interesting, opening the PDF again I can now see the previous page, but not the page I saw before.

It discusses a notable effect as long as "a" (the height of the opening) is relevant compared to H2. For a negligible hole size, and assuming we can adapt this to the vertical case, all the a/H terms vanish.
 
  • #66
mfb said:
Interesting, opening the PDF again I can now see the previous page, but not the page I saw before.

It discusses a notable effect as long as "a" (the height of the opening) is relevant compared to H2. For a negligible hole size, and assuming we can adapt this to the vertical case, all the a/H terms vanish.
Ok.
 

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