Question

Three identical blocks each of mass $m=1kg$ and volume $3\times {10}^{-4}{m}^3$ are suspended by massless string from a support as shown. Underneath are three identical containers containing the same amount of water that are placed over the scales. In Fig.4222 (a), the block is completely out of the water; in Fig. 4.222(b), the block in completely submerged but not touching the beaker and in Fig. 4.222(c), the block rests on the bottom of the beaker. The scale in Fig. 4.222(a). The scale in Fig. 4.222(a) reads $14N$.

• A. The tension in the string in (b) is $10N$
• B. The tension in the string in (b) is $7N$
• C. The reading of the scale in (b) is $17N$
• D. The reading of the scale in (c) is $24N$

Answer 1

Answer: (B), (C), (D)

The correct options are
B The reading of the scale in (b) is $17N$
C The reading of the scale in (c) is $24N$
D The tension in the string in (b) is $7N$

$\text{In figure (b), buoyant acting on the block}=Vpg$

$=3\times {10}^{-4}\times {10}^3\times 10N$

$=3N$

Forces acting on the block balance, thus

$mg=B+T$

$\Rightarrow T=mg-B=(10-3)N$

$=7N$