Question

A block of wood weights 12 kg and has a relative density 0.6. It is to be 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

The correct option is C 6 kg

Let the weight of metal required will be m

Volume of metal $=\frac{m}{14}$, as density is $14$

Weight of wood $=12kg$

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

Thus, total volume , $=20+\frac{m}{14}$

Now, Weight = buoyant force

So, the volume displaced will be for the wood only:

$(m+12)\times g=(0.9\times 20)\times g$ $\left(gisgravitationalacceleration\right)$

$m=18–12=6Kg$

Thus option C is correct.