Question 2
If the upthrust acting on an object when it is fully immersed in a fluid is less than its weight, what happens?
The right answer is the one marked above.
The object sinks in the fluid. The resultant force that remains acts downwards, so the object descends to the bottom.
If the upthrust equals the weight it floats fully immersed, and if the upthrust exceeds the weight it rises and floats partly immersed.