Question

In: Physics

A block of wood of uniform density floats so that exactly three-quarters if it’s volume is...

A block of wood of uniform density floats so that exactly three-quarters if it’s volume is underwater. The density of water is 1000 kg/m^3. What is the density of the block?

Solutions

Expert Solution

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


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