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Question
A wooden cube of side 10 cm has mass 700 g. What part of it remains above the water surface while floating vertically on water surface?
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Solution
Given, Side of wooden cube = 10 cm
Hence, Volume of wooden cube = 10 cm × 10 cm × 10 cm = 1000 cm3
Mass = 700 g
Density = `"mass"/"volume"`
∴ Density of wooden cube = `700/1000` = 0.7 g cm-3
By the principle of floatation,
`"Volume of immersed part"/"Total volume" = "Density of wood"/"Density of water"`
Density of water = 1 g cm-3
Density of wooden cube = 0.7 g cm-3
∴ `"Volume of immersed part"/"Total volume" = 0.7/1`
Hence, fraction submerged = 0.7
Height of wooden cube = 10 cm
Part of wooden cube which is submerged = 10 x 0.7 = 7 cm
Therefore, part above water = 10 - 7 = 3 cm
Hence, 3 cm of height of wooden cube remains above water while floating.
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