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Sir pls solve the following.
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Asked by rsudipto | 03 Jan, 2019, 13:02: PM
answered-by-expert Expert Answer
Loss of thermal energy for the water when it is cooled for every ΔT=5°C = m×Cp×ΔT Joules
radiated thermal power from water when it is cooled from 75° C to 70° C = σA(754 - 704) Watts
hence time taken to cool from 75° C to 70° C = begin mathsize 12px style fraction numerator m C subscript P increment T over denominator sigma A open parentheses 75 to the power of 4 space minus space 70 to the power of 4 close parentheses end fraction space equals space T subscript 1 cross times 60 space s end style
( we are given that this time is T1 minutes)
 
Hence T1 begin mathsize 12px style proportional to end style 1/(754 - 704 )
similarly we can write, T2 begin mathsize 12px style proportional to end style 1/(704 - 654 )
similarly we can write, T3 begin mathsize 12px style proportional to end style 1/(654 - 604 )
Hence it is obvious that T1 < T2 < T3
Answered by Thiyagarajan K | 03 Jan, 2019, 14:46: PM

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