Raising Shipwreck with Buoyancy Balloons - Calculations Needed?

  • Context: Undergrad 
  • Thread starter Thread starter gloo
  • Start date Start date
  • Tags Tags
    Air
Click For Summary

Discussion Overview

The discussion revolves around the calculations needed to determine the number of buoyancy balloons required to raise a shipwreck to the surface. Participants explore the factors influencing buoyancy, including the weight of the ship, trapped water, and external water pressure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether to consider the weight of the ship, the mass of the water trapped inside, and the weight of the water above the ship when calculating the lifting force required.
  • Another participant argues that while the water above exerts pressure, the net effect on the ship is balanced by upward pressure, suggesting that this can be disregarded in calculations except for its impact on balloon volume.
  • A different participant cautions about the water trapped inside the ship, stating that it does not affect the lifting force requirement since it has its own buoyancy.
  • Another participant notes that the buoyancy of the metal in the ship should be subtracted from the lifting force requirement.
  • One participant clarifies that including the water in calculations is acceptable as long as both the additional weight and volume are accounted for.

Areas of Agreement / Disagreement

Participants express differing views on whether the weight of the water above the ship should be included in the calculations, leading to an unresolved discussion on the correct approach to determining the lifting force needed.

Contextual Notes

There are limitations regarding assumptions about buoyancy and pressure effects, as well as the dependence on definitions of weight and volume in the context of submerged objects.

gloo
Messages
261
Reaction score
2
If there is a shipwreck that i am trying to raise and i try to calculate the number of ballons to attach to the ship to raise it to the surface, do i have to just the weight of the ship given it's mass (all the steel it's made of; all the stuff inside...) and the mass of the water trapped in it? Assume it's a rectangular ship sitting upright - don't i need to calculate the weight of all the water directly above it all the way to the surface? That weighs down on the ship doesn't it?
 
Physics news on Phys.org
gloo said:
If there is a shipwreck that i am trying to raise and i try to calculate the number of ballons to attach to the ship to raise it to the surface, do i have to just the weight of the ship given it's mass (all the steel it's made of; all the stuff inside...) and the mass of the water trapped in it? Assume it's a rectangular ship sitting upright - don't i need to calculate the weight of all the water directly above it all the way to the surface? That weighs down on the ship doesn't it?

The water above the ship exerts a pressure on it, that is true, but the additional pressure force pushing it down is canceled by an additional pressure force acting up on the bottom of the ship. By this I mean that the net effect of the pressure force on the ship is the same no matter how deep it is. You can disregard it, except for the effect it will have on the volume of the balloons.

There will also be a viscous force from the surrounding water acting downward when the ship starts to rise, but this can only slow it, not stop it from rising.
 
Be careful about the water trapped inside it - since you aren't lifting the ship above the water, the water inside does not affect the lifting force requirement. It has its own buoyancy.

You also need to subtract the buoyancy of the metal in the ship from the lifting force requirement.
 
To be clear, you can include the water in the calculation, but as long as you include both the additional weight and additional volume, it will make to difference.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 3 ·
Replies
3
Views
9K
  • · Replies 14 ·
Replies
14
Views
10K
  • · Replies 23 ·
Replies
23
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 24 ·
Replies
24
Views
5K