# Physics

A doctor uses an insulated backpack to “hike in” vaccines to a rural village in Papua New Guinea that is too remote for vehicular traffic. The vaccines are kept cold by packing them in 10 kg of ice. If the backpack absorbs heat (leaks cold) at a rate of 12 J/s, how long will it be before the last of the ice melts?

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1. Allow enough time (t) for the absorbed heat to equal the heat necessary to melt 10 kg of ice.

(12 J/s) * t = (10,000 g)*(80 Cal/g)*4.184 J/Cal

Solve for t, in seconds

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posted by drwls

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