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NEET2017PhysicsThermal Properties of MatterActual

A body initially at 80^ C cools to 64^ C in 5 ~min and to 52^ C in 10 ~min . The temperature of the surrounding is

Options

  1. A26^ C
  2. B16^ C
  3. C36^ C
  4. D40^ C

Correct answer

B. 16^ C

Step-by-step solution

According to Newton's law of cooling ₁- ₂ t =K [ ₁+ ₂ 2 - ₀ ] In the first case, 80-64 5 =K [ 80+64 2 - ₀ ] or 3.2=K [72- ₀ ] In the second case, 64-52 5 =K [ 64+52 2 - ₀ ] or 2.4=K [58- ₀ ] Dividing (i) by (ii), we get 3.2 2.4 = 72- ₀ 58- ₀ or 185.6-3.2 ₀=172.8-2.4 ₀ or ₀=16^ C

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