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MHT CET 2026 (18 Apr, Shift 2) · Newton's Law of Cooling

Newton's Law of Cooling question from MHT CET 2026 (18 Apr, Shift 2)

Q2MHT CET 2026 · 18 APR · SHIFT 2Medium

Newton's Law of Cooling

A body cools from a temperature 3θ3\theta to 2θ2\theta in 10 minute. The room temperature is θ\theta. The temperature of the body at the end of the next 10 minute is 'xx'. Assuming that Newton's law of cooling is applicable, the value of 'xx' will be

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Answer: (c)

  1. Newton's law: T1−T2t=k(T1+T22−T0)\frac{T_1 - T_2}{t} = k\left(\frac{T_1 + T_2}{2} - T_0\right).
  2. First 10 min: 3θ−2θ10=k(2.5θ−θ)⇒k=115\frac{3\theta - 2\theta}{10} = k(2.5\theta - \theta) \Rightarrow k = \frac{1}{15} per min
  3. Next 10 min: 2θ−x10=115(2θ+x2−θ)=x30\frac{2\theta - x}{10} = \frac{1}{15}\left(\frac{2\theta + x}{2} - \theta\right) = \frac{x}{30}
  4. 2θ−x=x3⇒x=32θ2\theta - x = \frac{x}{3} \Rightarrow x = \frac{3}{2}\theta
  5. So the answer is (c) 32θ\frac{3}{2}\theta.
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