Questions

A metallic sphere cools from ${50}^{0}$C to ${40}^{0}$C in 300s. If atmospheric temperature around is ${20}^{0}$C, then the sphere’s temperature after the next 5 minutes will be close to :

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By Expert Faculty of Sri Chaitanya
a
350C
b
330C
c
280C
d
310C
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detailed solution

Correct option is B

Newton's Law of Cooling,  θ1−θ2t1−t2=kθ1+θ22−θsur⇒50−40300=k50+402−20⇒10300=k45−20−−−1Now, 40−θf300=k40+θf2−20−−−−−2Dividing1 by 2, 1040−θf=2540+θf2−20⇒1040−θf=25θf×2⇒θf=1003=330C

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