1.

Time in which a layer of ice of thickness 10 cm will increase by 5 cm on te surface of a pond when temperature of the surrounding is `-10^(@)C` coefficient of thermal conductivity of ice `K=0.005((Cal)/(cm-sec-.^(@)C))` and density `rho=0.9gram//cm^(3)` (L=80cal/g)A. 20 HoursB. 25 HoursC. 30 HoursD. 5 Hours

Answer» Correct Answer - B
Time taken by the layer of ice to increase its thickness by `x=x_(2)-x_(1)`
`t=(rhoL)/(2Ktheta)(x_(2)^(2)-x_(1)^(2))=(.9xx80)/(2xx.005xx10)[(15)^(2)-(10)^(2)]`
`t=9xx10^(4)sec,t=25` hours


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