CBSE Class 11-science Answered

From Newton's law of cooling , we get temperature T(t) as a function of time when it cools from initial temperature T_o is

T(t) = T_s + ( T_o - T_s ) e^{-k t} . ........................(1)

where T_s is temperature of surroundings .

If T(t) = 70^o C after t = 5 min = 300 s , then we get from eqn.(1) as

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When the object is cooling after reaching 70^o C , temperature after 5 minutes is calculated from eqn.(1)

When the object is cooling after reaching 56.7^o C , temperature after 5 minutes is calculated from eqn.(1)

Hence , temperature after 10 minutes when the object is colling from 70^o C is 47.8 ^oC