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Certain quantity of water cools from 70⁰ C to 60⁰C in the first 5 minutes and to 54⁰ C in the next 5 minutes. The temperature of the surroundings is
Options
(a) 45⁰ C
(b) 20⁰ C
(c) 42⁰ C
(d) 10⁰ C
Correct Answer:
45⁰ C
Explanation:
Let the temperature of surroundings be θ₀
By Newton’s law of cooling
(θ₁ – θ₂ / t) = k [(θ₁ – θ₂ / 2) – θ₀]
[(70 – 60) / 5] = k [(70 + 60 / 2) – θ₀] ⇒ 2 = k [65 – θ₀] ——(i)
Similarly, (60 – 54) / 5 = k = [(60 + 54 / 2) – θ₀]
6 / 5 = k [57 – θ₀] ——–(ii)
By dividing (i) by (ii) we have
10 / 6 = (65 – θ₀) / (57 – θ₀) ⇒ θ₀ = 45⁰
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Topics: Properties of Bulk Matter
(130)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The approxiamate ratio of nuclear mass densities of ₇₉Au¹⁹⁷ and ₄₇ Ag¹⁰⁷ nuclei is
- A coin of mass m and radius r having moment of inertia I about the axis passes
- A capacitor is used to store 24 watt hour of energy at 1200 volt.
- A point charge q is situated at a distance r on axis from one end of a thin
- For a thermocouple, the neutral temperature is 270⁰C when its cold junction is at 20⁰C.
Topics: Properties of Bulk Matter (130)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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