When does Bouyant Force change?

[September24]

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There are a lot of questions that ask, bouyant force on X increase or decreases.....and so on. I get confused because I can't figure out which item has more bouyant force or when certain things increase in bouyant force. For example.


Three objects are submerged underwater. They have same density but different volumes. Which one has most bouyant force.


Three objects are submerged underwater. They have same volume but different density. Which one has most bouyant force.

As an object descends under wall, does bouyant force change.

Questions like these confuse me. So far, the ONLY thing that change bouyant force is density of medium and volume of the object right?

 

[mehc012]

There are a lot of questions that ask, bouyant force on X increase or decreases.....and so on. I get confused because I can't figure out which item has more bouyant force or when certain things increase in bouyant force. For example.


Three objects are submerged underwater. They have same density but different volumes. Which one has most bouyant force.


Three objects are submerged underwater. They have same volume but different density. Which one has most bouyant force.

As an object descends under wall, does bouyant force change.

Questions like these confuse me. So far, the ONLY thing that change bouyant force is density of medium and volume of the object right?

Your last sentence pretty much has it right. The buoyant force = weight of the medium displaced. What changes that? Changing either the density of the medium or the volume that is displaced.

Changing the density of the object may change, in colloquial terms, how buoyant it is (whether it sinks, floats, stays), but that is a factor of whether the buoyant force is larger than the weight of the object, rather than the size of the buoyant force. To put it another way, a dense object and a light object of the same volume have the SAME buoyant force when submerged...but for one, the large gravitational pull overcomes the buoyant force and for the other, the buoyant force overcomes the small weight.

 

[MTHFR]

Right. From the equation for B, it only depends on the density of the medium, volume of the object, and the force of gravity (if they were comparing the B of an object, say, on the moon from an object on Earth).