Q 11-10-080JEE MainJEE Main 2022 (26 Jun, Shift 2)Easy
A geyser heats water flowing at a rate of $2.0\ \text{kg}$ per minute from $30^\circ\text{C}$ to $70^\circ\text{C}$. If the geyser operates on a gas burner, the rate of combustion of fuel will be ______ $\text{g min}^{-1}$. [Heat of combustion $= 8\times10^3\ \text{J g}^{-1}$, specific heat of water $= 4.2\ \text{J g}^{-1}\,^\circ\text{C}^{-1}$]
Numerical value type. Enter your answer.
Answer: 42
Heat needed per minute: $2000\times4.2\times40 = 3.36\times10^5\ \text{J}$.
$$\text{Fuel rate} = \frac{3.36\times10^5}{8\times10^3} = 42\ \text{g min}^{-1}$$
Solution by Sreeraj P, M.Sc Physics