Question 4
By Archimedes' principle, what is the upthrust on an object immersed partly or wholly in a fluid equal to?
The right answer is the one marked above.
The weight of the fluid displaced by the object. This holds whether the object floats or sinks.
The displaced volume is a volume, not a force, so it cannot equal one. And the upthrust equals the object's weight only when the object floats, not in every case.