A body takes 4 min. to cool from 61$^\circ$ C to 59$^\circ$ C. If the temperature of the surroundings is 30$^\circ$ C, the time taken by the body to cool from 51$^\circ$ C to 49$^\circ$ C is :
Solution
${{\Delta T} \over {\Delta t}} = K({T_t} - {T_s})$<br><br>T<sub>t</sub> = average temp.<br><br><sub>T</sub> = surrounding temp.<br><br>${{61 - 59} \over 4} = K\left( {{{61 + 59} \over 2} - 30} \right)$ ..... (1)<br><br>${{51 - 49} \over t} = K\left( {{{51 + 49} \over 2} - 30} \right)$ ..... (2)<br><br>Divide (1) & (2)<br><br>${t \over 4} = {{60 - 30} \over {50 - 30}} = {{30} \over {20}}$<br><br>So, t = 6 minutes.
About this question
Subject: Physics · Chapter: Properties of Solids and Liquids · Topic: Elasticity
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