A log of wood of mass $120 Kg$ floats in water. The weight that can be put on the raft to make it just sink, should be ....... $Kg$ (density of wood = $600 Kg/m^3$)
A$80 $
B$50 $
C$60 $
D$30 $
Diffcult
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A$80 $
a (a) Volume of log of wood $V = \frac{{{\rm{mass}}}}{{{\rm{density}}}} = \frac{{120}}{{600}}=0.2 m^3$
Let x weight that can be put on the log of wood.
So weight of the body = $(120 + x) \times 10\;N$
Weight of displaced liquid = $V\sigma g = 0.2 \times {10^3} \times 10\;N$
The body will just sink in liquid if the weight of the body will be equal to the weight of displaced liquid.
$(120 + x) \times 10 = 0.2 \times {10^3} \times 10$
$ \Rightarrow \;120 + x = 200$
$x = 80 kg$
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