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Chapter 14: Q20Q (page 390)
A 22°C day is warm, while a swimming pool at 22°C feels cool. Why?
The rate of heat flow is more when you are in the pool. So, it feels cooler inside the pool than the land at the same temperature.
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Goose down sleeping bags and parkas are often specified as so many inches or centimeters of loft, the actual thickness of the garment when it is fluffed up. Explain.
Why is wet sand at a beach cooler to walk on than dry sand?
(III) Approximately how long should it take 8.2 kg of ice at 0°C to melt when it is placed in a carefully sealed Styrofoam ice chest of dimensions \({\bf{25}}\;{\bf{cm \times 35}}\;{\bf{cm \times 55}}\;{\bf{cm}}\) whose walls are 1.5 cm thick? Assume that the conductivity of Styrofoam is double that of air and that the outside temperature is 34°C.
Estimate the rate at which heat can be conducted from the interior of the body to the surface. As a model, assume that the thickness of tissue is 4.0 cm, that the skin is at 34°C and the interior at 37°C, and that the surface area \({\bf{1}}{\bf{.5}}\;{{\bf{m}}{\bf{2}}}\) is Compare this to the measured value of about 230 W that must be dissipated by a person working lightly. This clearly shows the necessity of convective cooling by the blood.
Ceiling fans are sometimes reversible, so that they drive the air down in one season and pull it up in another season. Explain which way you should set the fan (a) for summer, (b) for winter.
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