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Question
A block of wood of volume 25 cm3 floats in water with 20 cm3 of its volume immersed in water.
Calculate:
(1) density of wood
(2) the weight of block of wood.
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Solution
Volume of wooden block = V = 25 cm3
Volume of wooden block immersed in water = 20 cm3
Volume of water displaced by wooden block=volume of wooden
block immersed in water = 20 cm3
Density of water = ρwater = 1 gcm-3
Density of wooden block =ρwood = ?
By law of floatation:
volume of wooden block x Density of wood=Volume of water displaced x Density of water
`25 xx rho_"wood" = 20 xx 1`
`rho_"wood" = 20/25 = 0.8` g cm-3
Weight of wooden block `"V"rho_"wood""g"`
= 25 × 0.8 × g = 20 gf
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