Posted by **Momito** on Saturday, April 7, 2012 at 4:00pm.

A rectangular block of wood is 40cm wide, 60cm long and 30cm deep. If its relative density is 0.7kg/m^3 and it floats with its 30cm side vertical, determine: a)the length of the block above the water surface and b)the minimum force required to completely submerge the block

- Physics -
**Elena**, Saturday, April 7, 2012 at 4:50pm
W =0.4 m , L = 0.6 m , H = 0.3 m, ρ1 is the density of wood, ρ2 is the density of the liquid,

relative density is ρ1/ ρ 2 = 0.7 (dimensionless quantity!!!)

m•g = F (buoyant)

m•g = ρ1• V•g = ρ1•W•L•H•g,

F (buoyant) = ρ2• V1•g =

= ρ2•W•L•(H-x)•g.

ρ1•W•L•H•g = ρ2•W•L•(H-x)•g,

ρ1• H = ρ2• (H-x),

x = H•( (ρ1/ ρ2) – 1) =

= 0.3•( (1/0.7) – 1) = 0.129 m.

- Physics -
**Elena**, Saturday, April 7, 2012 at 4:58pm
F + mg=F(buoyant)

F = F(buoyant) - mg = ρ2•W•L•H•g – ρ1•W•L•H•g = W•L•H•g•(ρ2– ρ1)

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