Question

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 (density of wood=600Kg/m³)

• A. 80 Kg
• B. 50 Kg
• C. 60 Kg
• D. 30 Kg

Answer 1

The correct option is A

80 Kg

Volume of log of wood $V=\frac{mass}{density}=\frac{120}{600}=0.2m^3$

Let x weight that can be put on the log of wood.

So weight of the body = $(120+x)\times 10N$

Weight of displaced liquid = $V\rho g=0.2\times {10}^3\times 10N$

The body will just sink in liquid if the weight of the body will be equal to the weight of displaced liquid.

$(120+x)\times 10N=0.2\times {10}^3\times 10N$
$\Rightarrow x=80kg$