JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Fluid Mechanics

A tube is filled with water and a wooden cube

10 cm \times 10 cm \times 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 / cm^{3}

and density of wood as

0.4 g / cm^{3}

)

Answer: 387

Solution

When the coin is added, the extra buoyant force must support its weight:

m_{c} g = ρ_{w} g Δ V

, where

Δ V

is the additional submerged volume. With the

10 cm \times 10 cm

base sinking a further

3.87

cm,

Δ V = 100 \times 3.87 = 387 c m^{3}

. Hence

m_{c} = ρ_{w} Δ V = 1 \times 387 = 387

g. The mass of the metal coin is

387

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Integer answer

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