Properties Of Solids And Liquids Question 453
Question: A body cools from $ 50.0{}^\circ C $ to $ 49.9{}^\circ C $ in 5s. How long will it take to cool from $ 40.0{}^\circ C $ to$ 39.9{}^\circ C $ ? Assume the temperature of surroundings to be $ 30.0{}^\circ C $ and Newton’s law of cooling to be valid
Options:
A) 2.5 s
B) 10 s
C) 20 s
D) 5 s
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ \frac{50-49.9}{t}=K( \frac{50+49.9}{2}-30 ) $ ….(i)
$ \frac{40-39.9}{t}=K[ \frac{40+39.9}{2}-30 ] $ -(ii)
From equations (i) and (ii), we get$ t\approx 10 s $ .
