On a hot summer day, surface of the concrete highway may reach 328 K. Suppose a stream of water is directed on the highway so that the surface is suddenly lowered to 308 K. Time taken in hours to cool the concrete to 318 K to a depth of 5 cm below the surface is: (Thermal diffusivity = 1.77 × 10-3 m2/hr).

On a hot summer day, surface of the concrete highway may reach 328 K.

1.	On a hot summer day, surface of the concrete highway may reach 328 K. Suppose a stream of water is directed on the highway so that the surface is suddenly lowered to 308 K. Time taken in hours to cool the concrete to 318 K to a depth of 5 cm below the surface is: (Thermal diffusivity = 1.77 × 10-3 m2/hr).
A.	1.2
B.	1.4
C.	1.6
D.	1.8
Answer» C. 1.6

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