Does density affect the buoyancy of submerged objects?

[Velouria555]

Homework Statement

We fully submerge an irregular 3 kg lump of material in a certain fluid. The fluid that would have been in the space now occupied by the lump has a mass of 2 kg. a) When we release the lump, does it move upward, downward, or remain in place? b) If we next fully submerge it in less dense fluid and again release it, what does it do?

Homework Equations

F_b=m_fg

The Attempt at a Solution

For a) I just assumed that F_g is > _b since the mass of the lump is greater than the mass of the water displaced.
I know that for b) it also goes downward, but why? Does density simply not matter because it's not factored into the equation for buoyancy or would the result be different if we submerged the lump in a fluid that is more dense?

 

[Suraj M]

What are the factors buoyant force is dependent on ? and what factors remain constant when when we use a less or more dense liquid instead of the one we are using now?

 

[Velouria555]

What are the factors buoyant force is dependent on and what factors remain constant when when we use a less or more dense liquid instead of the one we are using now

Well, F_b is dependent on mass of the fluid and g. Mass=ρV.. So as density of the fluid increases, so does its mass and therefore, its buoyancy? But if it decreases, the mass decreases as well so F_g will be even greater than F_b and the object will definitely go downward...? Is this correct?

Btw, thanks for the help!

 

[haruspex]

Well, F_b is dependent on mass of the fluid and g. Mass=ρV.. So as density of the fluid increases, so does its mass and therefore, its buoyancy? But if it decreases, the mass decreases as well so F_g will be even greater than F_b and the object will definitely go downward...? Is this correct?

Yes. What is the borderline case?

 

[Suraj M]

Your answer is right, I was just responding to this

Does density simply not matter because it's not factored into the equation for buoyancy or would the result be different if we submerged the lump in a fluid that is more dense?

Hope you got your answer.

 

[Velouria555]

Yes. What is the borderline case?

Hi haruspex! Sorry, I'm not sure that I understand. Borderline case as in...?

 

[Velouria555]

Your answer is right, I was just responding to this


Hope you got your answer.

I believe so, thanks for your help! Sometimes I feel completely certain I know how to solve a problem in physics only to be totally wrong so I appreciate your confirmation that I was going in the right direction :)

 

[Suraj M]

Hi haruspex! Sorry, I'm not sure that I understand. Borderline case as in...?

You considered a case where density is more than or less than then that leaves out a borderline case right? Something in between?