AS Daily A Level Physics question
An irregular metal ornament is hung from a newton meter. The reading is 6.0 N in air. When fully immersed in fresh water the reading is 5.3 N, and when fully immersed in a different liquid the reading is 5.0 N. Which statement must be true?
Answer
The correct answer is B.
Correct: B — The second liquid has a greater density than water. A lower meter reading means a larger upthrust; for the same fully submerged object (same displaced volume), a larger upthrust implies a higher fluid density. A The object is fully submerged in both cases, so it displaces its own volume in each liquid, not more in the second. B This is correct because the greater reduction in reading indicates a larger upthrust due to the higher-density liquid. C The object’s weight does not change between media; only the apparent weight changes due to upthrust. D The change in reading equals the upthrust (the weight of displaced fluid), not the object’s volume; confusing these ignores the role of fluid density and units.