Question

A block of wood of mass 24 kg floats on water. The volume of wood is 0.032 m3.
Find —
(a) the volume of block below the surface of water,
(b) the density of wood.
(Density of water = 1000 kg m-3)

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Answer

Mass = 24 kg

Volume = 0.032 m3

Upthrust = Volume of the block below the water × density of liquid × acceleration due to gravity

24 × g = v × 1000 × g

⇒ v = 24/over 1000 = 0.024 m3

Hence, the volume of the block below the surface of water = 0.024 m3

(b) By the principle of floatation,

{0.024\over 0.032}={Density\ of\ wood\over 1000}

⇒ Density of wood = {0.024\over 0.032}× 1000 = 7500 kg m-3

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