Working with archimedes principle.

[vkash]

Homework Statement

Consider a submarine inside an ocean. It's bottom is flat and upper portion is hemispherical. It is settled at the bottom of the sea. What should direction of Boyant force. Upward or downward? Now by the external agent the submarine is lifted a bit up. Now it is not touching the surface of the sea. What will be direction of boyant force in this case.

Homework Equations

upthrust is equal to weight of liquid displaced.
Mainly it is dF=P.dA.

The Attempt at a Solution

I think the direction of boyant force(boyant doesn't seems to be correct word) in first case is in downward and in second case it is upward direction.
Am i correct?

 

[JHamm]

Well what is your reasoning?

 

[vkash]

Well what is your reasoning?

Oh yes i have reasons
In short it is ∫P.dA.
In first case pressure is applied from above the submarine. Since force is perpendicular to surface so should sum up to give net force in downward direction.
In second case it's too long to explain. IT is similar in case when a body is fully inside liquid.


I post this question because it related to a question in my book that is something like this.
There are two immersible liquid of relative density 1.5 and 2.5. There is an object of relative density 2 What is percentage volume inside the liquid of relative density 1.5 & 2.5.

 

[JHamm]

You're correct but I don't see how that problem helps you with your book's question?

 

[vkash]

You're correct but I don't see how that problem helps you with your book's question?

Oh you did not found the link.
SO tell me what will direction of force applied by liquid above the object. that is partially dipped in upper liquid as i have presented in first example.

Do you have any good method to solve this question?(question is in my last post)

 

[JHamm]

So you have two bowls with a liquid in each with relative densities of 1.5 and 2.5 each and you drop an identical object in each one and you want to find how much of the object sits below the surface of each liquid?