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QPages 98-102: Q51: HC Verma: Concepts of Physics - Volume 2 Heat Transfer Pages 98-102: Q51 Solution: A body cools down from 50�C to 45�C in 5 minutes and to 40�C in …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often replace the exponential law $T(t)=T_s+(T_0-T_s)e^{-kt}$ with a linear relation $(\Delta T)/\Delta t = k(\overline{T}-T_s)$, using the average temperature over the interval. This yields incorrect algebra; instead set up the exact exponential equations for each time span and solve for $T_s$ and $k$.

A body cools down from 50�C to 45�C in 5 minutes and to 40�C in another 8 minutes. Find the temperature of the surrounding.

Step-by-Step Verified Solution

**Answer:** Surrounding temperature = 22.8�C. **Step-BY-Step Explanation:** Using Newton's law: (50_45)/5 = k(47.5_T_) and (45_40)/8 = k(42.5_T_). Dividing: 1/5 / 5/8 = (47.5_T_)/(42.5_T_) _ T_ = 22.8�C.

All Questions in this Chapter

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