A tank holds 0.5 m³ of water, kept at 60°C by a 2 kW heater in a room at 20°C. The heater is switched off. Find the time for the water to cool to 40°C, in hours. Use Newton\'s law without averagi

Question

A tank holds 0.5 m³ of water, kept at 60°C by a 2 kW heater in a room at 20°C. The heater is switched off. Find the time for the water to cool to 40°C, in hours. Use Newton\'s law without averaging, c = 4200 J kg⁻¹ K⁻¹.

TestHub · Accepted Answer

k = 40 2000 ​ = 50 W/K, C = 500 × 4200 = 2.1 × 1 0 6 J/K. t = k C ​ ln 20 40 ​ = 42000 × 0.693 = 29112 s = 8.09 h.

Physics - Heat & Thermo Question with Solution | TestHub

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