NEET 2019 Odisha · PhysicsPrevious Year Question
An object kept in a large room (air temperature 25 °C) takes 12 minutes to cool from 80 °C to 70 °C. The time taken by the same object to cool from 70 °C to 60 °C would be nearly:
Answer: (D) 15 min. (ΔT/time) = k(T_avg − 25).
- A.10 min
- B.12 min
- C.20 min
- D.15 min✓
Correct Answer
(D) 15 min
Solution & Explanation
(ΔT/time) = k(T_avg − 25). 80→70: 10/12 = k(75 − 25) = 50k ⇒ k = 1/60. 70→60: 10/t = k(65 − 25) = 40k = 40/60 = 2/3 ⇒ t = 15 min.
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