The ratio of masses of a cubical block of wood and a chunk of concrete is 3/5 so that the combination just floats with entire volume submerged under water. If the specific gravity of wood is 0.5, then specific gravity of concrete will be

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The ratio of masses of a cubical block of wood and a chunk of concrete is 3/5 so that the combination just floats with entire volume submerged under water. If the specific gravity of wood is 0.5, then specific gravity of concrete will be

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ρ_av = ρ_water
$\frac{m_{C} + m_{w}}{v_{C} + v_{w}}$ = 1
$\frac{m_{w}}{m_{C}} = \frac{3}{5}$
m_C = $\frac{5 mw}{3}$

$\frac{8}{3}$ m_w = v_C + v_w
$\Rightarrow \frac{8}{3}$ × 0.5v_w = v_C + v_w
$\Rightarrow \frac{1}{3}$ v_w = v_C
$\frac{m_{C}}{v_{C}} = \frac{\frac{5}{3} m_{w}}{v_{w}}$ = 5 × 0.5 = 2.5