Question:
An aluminium vessel of mass $0.5 \mathrm{~kg}$ contains $0.2 \mathrm{~kg}$ of water at $20^{\circ} \mathrm{C}$. A block of iron of mass $0.2 \mathrm{~kg}$ at $100^{\circ} \mathrm{C}$ is gently put into the water. Find the equilibrium temperature of the mixture. Specific heat capacities of aluminium, iron and water are $910 \mathrm{~J} / \mathrm{kg}-\mathrm{K}, 470 \mathrm{~J} / \mathrm{kg}-\mathrm{K}$ and $4200 \mathrm{~J} / \mathrm{kg}-\mathrm{K}$ respectively.
Solution:
