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JEE Main20203 Sep 2020Evening ShiftPhysicsThermal Properties of MatterActual

A metallic sphere cools from 50 ° C to 40 ° C in 300 s . If atmospheric temperature around is 20 ° C , then the sphere's temperature after the nest 5 minutes will be close to:

Options

  1. A31   ° C
  2. B33   ° C
  3. C28   ° C
  4. D35   ° C

Correct answer

B. 33   ° C

Step-by-step solution

Using Newton's Law of cooling 50 - 40 5   min = K 50 + 40 2 - 20 ......(i) Next 5   min . 40 - θ 5 = K 40 + θ 2 - 20 .....(ii) Dividing (ii)/(i) 40 - θ 10 = 40 + θ - 40 50 + 40 - 40 = θ 50 40 - θ = θ 5 200 - 5 θ = θ ∴       θ = 200 6 = 33 . 3   ° C

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