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On a winter day the air temperature falls to -10 deg C and ice forms on a lake whose water is already at 0 deg C. Using density of water = 1000 kg/m³, latent heat of fusion of ice = 3.36 x 10⁵ J/kg and thermal conductivity of ice = 1.7 W/m/deg C (neglecting expansion on freezing), find the approximate time to form a 10 cm thick ice layer.

1. 27 hours
2. 13 hours
3. 22 hours
4. 17 hours

Correct answer: 27 hours

Solution

Substituting the values gives about 9.88 x 10⁴ s, roughly 27 hours.

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