Question

An ornament weighing 150 g in air weight only 76 g in water. Assuming that some copper is mixed with gold to prepare the ornament. The amount of copper in it specific gravity of gold is 20 and that of copper is 10.

Answer 1

Mass of ornament in air = 150 gm

Mass of ornament in water = 76 gm

Density of gold = 20 gm/cc

Density of copper = 10 gm/cc

Specific gravity is the ratio of the density of a substance to the density of a reference substance

Density of gold = 20 gm/cc

Density of copper = 10 gm/cc

Loss in weight = 150 – 76 = 74 gm

If $m_g$ is the mass of gold and $m_c$ is the mass of copper and $V_g$ and $V_c$ are their respective volumes;

$m_g+m_c=\mathrm{150............}\left(1\right)$

$74=V_g+V_c$

$74=\frac{m_g}{20}+\frac{m_c}{10}$

$74=\frac{m_g+2m_c}{20}$

$1480=m_g+2m_c............\left(2\right)$

Now solving equation (1) and (2)

$m_c=1330gm$