A tub is filled with water and a wooden cube 10 cm × 10 cm × 10 cm is placed in the water. The wooden cube is found to float on the water with a part of it submerged in water. When a metal coin is placed on the wooden cube, the submerged part is increased by 3.87 cm. The mass of the metal coin is ________ gram.
(Take water density as 1 g/cm³ and density of wood as 0.4 g/cm³)
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JEE Main 2026 · 2 Apr · Shift 1, Physics question 50
Answer and worked solution
Official answer: 387
Extra buoyancy. The coin's weight equals the weight of the extra water displaced: cm³ of water, i.e. 387 g.
Check. The cube first floats 4 cm deep (density 0.4) and then 7.87 cm < 10 cm, so it still floats.
Answer: 387