Question

A raft 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 $\left(d_{ \text{raft} }=600\, kg / m ^{3}\right)$

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

Answer 1

Answer: (A)

80 kg

Answer 2

Volume of raft is given by $V=\frac{m}{d}=\frac{120}{600}=0.2\, m ^{3}$ If the raft is immersed fully in water. Then weight of water displaced is $=V d_{\text {water }}$ $=0.2 \times 10^{3}=200 \,kg$ Hence, the additional weight which is supported by raft $=200\, kg -120\, kg =80\, kg$