Question

A block of wood weights 12 kg and has a relative density 0.6. It is to be in water with 0.9 of its volume immersed. What weight of a metal is needed if the metal is on the top of wood? [Relative density of metal = 14]

• A. 2 kg
• B. 4 kg
• C. 6 kg
• D. 8 kg

Answer 1

Answer: (C)

6 kg

Let the weight of metal needed be $m$

volume of metal $=m/14$

Weight of wood $=12kg$

volume of wood $=\frac{12}{0.6}=20$

Total volume $=20+\frac{m}{14}$

Now, Weight = Bouayant force

The volume displaced will be of only of wood

$=>(m+12)g=g(0.9\times 20)$

$=>m=6Kg$