Challenge GC Q

[SonhosDaVida]

So Q13 says that the compound in argon gas will have a greater buoyant force than the compound in nitrogen air. I agree with this, since heavier compound s have greater buoyant forces.

But the compound is weighed in a scale, so doesn't that mean the (rho)Vg=mg since the object won't be floating? Thus a greater density will correlate to s greater mass read on the scale instead of less mass if u cancel out g to get rhoV=m

This is not the answer. The andwer says the object has a lower apparent weight on scale.

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[AdaptPrep]

Hi, SonhosDaVida--

The buoyant force upwards that the object being weighed experiences is equal to the weight force of the volume of air/argon displaced by that object. The volume of the object is the same in air or in argon; therefore, the volume of displaced atmosphere is the same. However, the mass of this displaced atmosphere is not the same--argon has a larger mass and hence, a larger weight force. That weight force is equal to the buoyant force which is directed upwards. This buoyant force "lifts" the object on the scale to a greater extent than air would lift it. The formula you used would give the buoyant force (density * V * gravity) since it is the volume and weight force of the atmosphere displaced (the density and mass are of the atmosphere and not of the object being weighed).

I hope that helps.