the buoyant force...suppose an object weight 3n in the air but 2n in water, what is the buoyant force?

Question

is it 4?

Answer 1

Weight of a body ,when weighed in a liquid=( weight of body in air ) - ( upthrust on the body )

Upthrust=( wt. in air ) - (wt. in liquid)

Buoyant force=upthrust= ( wt. in air ) - (wt. in liquid)


[Loss in weight of a body when it is weighed in a liquid is equal to buoyant force on the body]

Buoyant force = 3 newton - 2 newton= 1 newton

Buoyant force on the body = 1 newton

Answer 2

Buoyant force is the force from a fluid acting on an object submerged in that fluid. If an object weighs 3 N in the air, but its effective weight is only 2 N in water, something must be pushing that object in a direction opposite to the force of gravity. That something is buoyant force; it's pushing up against the weight of the object to give the effective weight in water as 2 N.

If W = weight in air and B = bouyant force pushing up in an opposite direction to W, then w = W - B = the effective weight of the object while submerged in a fluid (e.g., water). Thus, w = W - B = 3 - B = 2; so that B = 3 - 2 = 1 N, which is the force of buoyancy in your case.

Now let me ask you a question. if w = W - B = 0, is that object floating or sinking in that water? That is, if the buoyancy is equal, but opposite to the air weight of the object so the effective weight is zero, will that object float or sink?