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Two cubes, each of side 1.0 m, are tied together with a weightless string. One cube has relative density 0.60 and the other has relative density 1.15. The pair is placed in a large tank of water. In equilibrium, by what height does the lighter cube project above the water surface?
- 50 cm
- 25 cm
- 10 cm
- zero
Correct answer: 25 cm
Solution
The heavier cube (RD 1.15) sinks and is fully submerged. The lighter cube (RD 0.60) is partly out. For the combined system, total weight equals buoyant force on both cubes. Solving gives the submerged depth of the lighter cube, and the exposed height is the remainder.
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