Question

The temperature of $600$ g of cold water rises by $15$${}^{\circ }$C, when $300$ g of hot water $50$${}^{\circ }$C is added to it. What was the initial temperature of the cold water?

• A. 10${}^{\circ }$C
• B. 15${}^{\circ }$C
• C. 5${}^{\circ }$C
• D. 25${}^{\circ }$C

Answer 1

Answer: (C)

5${}^{\circ }$C

let the final temperature be $T$

Heat absorbed by water=Heat given by water

$Q=mc\Delta T$

$\Rightarrow 600\times 4.2\times 15=300\times 4.2\times (50-T)$

$\Rightarrow T={20}^{o}C$

So initial temperature of cold body $=20-15$

$=5^{o}C$