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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Thermal Properties of Matter

NTA Abhyas 2020 · Physics · Thermal Properties of Matter

The temperature of a liquid drops from 365K to 361K in 2minutes ....

The temperature of a liquid drops from 365K365K to 361K361Kin 2minutes2minutes. The time during which temperature of the liquid drops from 344K344K to 342K342K is (Room temperature is 293K293K) -

Options

  1. A84s84s
  2. B72s72s
  3. C66s66s
  4. D60s60s

Correct answer

A. 84s84s

Step-by-step solution

From Newton's law of cooling,

365−3612=K(365+3612−293)\dfrac{365 - 361}{2} = K \left(\dfrac{365 + 361}{2} -293\right) ..... (1)

344−342t=\dfrac{344 - 342}{t} = K \left(\dfrac{344 + 342}{2} -293\right)....(2)<br/><br/>Equation(1)÷(2).... (2)<br /><br />Equation \left(1\right) \div ( 2 )

t=365+361−586344+342−586=140100mint = \dfrac{365 + 361 - 586}{344 + 342 - 586} = \dfrac{140}{100}min

= \dfrac{140 \times 60}{100}s= 84s
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