Thermal Properties of Matter - Result Question 49

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50. A body cools from $50.0^{\circ} C$ to $48^{\circ} C$ in $5 s$. How long will it take to cool from $40.0^{\circ} C$ to $39^{\circ} C$ ? Assume the temperature of surroundings to be $30.0^{\circ} C$ and Newton’s law of cooling to be valid.

======= ####50. A body cools from $50.0^{\circ} C$ to $48^{\circ} C$ in $5 s$. How long will it take to cool from $40.0^{\circ} C$ to $39^{\circ} C$ ? Assume the temperature of surroundings to be $30.0^{\circ} C$ and Newton’s law of cooling to be valid.

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/thermal-properties-of-matter/thermal-properties-of-matter—result-question-49.md (a) $2.5 s$

(b) $10 s$

(c) $20 s$

(d) $5 s$

[1994]

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Answer:

Correct Answer: 50. (b)

Solution:

  1. (b) Rate of cooling $\propto$ temperature difference between system and surrounding.

As the temperature difference is halved, so the rate of cooling will also be halved.

So time taken will be doubled

$t=2 \times 5$ sec. $=10$ sec.