In: Physics
b
= density of the block
w
= density of the water = 1000 kg/m3
V = Volume of the block
mass of the block is given as
m = mass of block = Volume x density
m =
b
V
eq-1
V' = Volume of the block inside the water = 3V/4 = 0.75 V
force of buoyancy on the block is given as
Fb =
w V' g
Fb = (0.75)w
V
g
eq-2
since the block is floating , the force of buoyancy in upward direction balances the weight in down direction
Fb = Fg
using eq-2 and eq-1
(0.75)w
V g = mg
(0.75)w
V g =
b Vg
b
= (0.75)
w
b
= (0.75) (1000)
b
= 750 kg/m3