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Physics · PYQ NEET UG 2019(2)
हिन्दीAn object kept in a large room having air temperature of \( 25^\circ\text{C} \) takes \( 12\text{ minutes} \) to cool from \( 80^\circ\text{C} \) to \( 70^\circ\text{C} \). The time taken to cool for the same object from \( 70^\circ\text{C} \) to \( 60^\circ\text{C} \) would be nearly,
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Correct answer · Option A
15 min
Explanation
Using Newton's Law of Cooling \( \frac{T_1 - T_2}{t} = K (\frac{T_1+T_2}{2} - T_s) \). For first interval: \( \frac{80-70}{12} = K (75 - 25) \implies \frac{10}{12} = 50K \). For second interval: \( \frac{70-60}{t'} = K (65 - 25) \implies \frac{10}{t'} = 40K \). Taking ratio, \( \frac{t'}{12} = \frac{50}{40} \implies t' = 15\text{ min} \).
