A 1.88-m (6 ft 2 in.) man has a mass of 81 kg, a body surface area of 1.8 m², and a skin temperature of 36.8 °C. You model his emissivity e to be 1 because his body radiates almost entirely infrared energy, which is not affected by skin pigment. In addition, your model assumes that he loses heat only through radiation. According to your model, how many food calories should he eat per day to keep his body temperature constant in a room at 20.0 °C. (Careful: The environment also radiates back into his body. The net rate of radiation is Pnet - Phody - Penvironment.) = food calories per day = 1.59 x107 Incement C/day

A 1.88-m (6 ft 2 in.) man has a mass of 81 kg, a body surface area of 1.8 m², and a skin temperature of 36.8 °C. You model his emissivity e to be 1 because his body radiates almost entirely infrared energy, which is not affected by skin pigment. In addition, your model assumes that he loses heat only through radiation. According to your model, how many food calories should he eat per day to keep his body temperature constant in a room at 20.0 °C. (Careful: The environment also radiates back into his body. The net rate of radiation is Pnet - Phody - Penvironment.) = food calories per day = 1.59 x107 Incement C/day

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 44P: What are the following temperatures on the Kelvin scale? (a) 68.0 F, an indoor temperature sometimes...

See similar textbooks

Similar questions

(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I .40-m surface area? Assume that the animal's skin temperature is 32.0 , that the air temperature is 5.00 , and that has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?
The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m K and 0.020 W/m K, respectively, while other tissues inside the body have conductivities of about 0.50 W/m K. Assume that between the core region of the body and the skin sin face lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. (b) Find the rate of energy loss when the core temperature is 37C and the exterior temperature is 0C. Assume that both a protective layer of clothing and an insulating layer of unmoving air a absent, and a body area of 2.0 m2.
One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose a single-story cubical house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, by what percentage would the heating cost of the house drop? Take the house to have dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors, and assume that the interior is uniformly at one temperature and the exterior is uniformly at another.
(a) If the partial pressure of water vapor is 8.05 torr, what is the dew point? (760 torr = I atm 101, 325 Pa) (b) On a warn day when the air temperature is 35 and the dew point is 25 , what are the partial of the water in the air and the relative humidity?
An astronaut performing an extra-vehicular activity (space walk) shaded from the Sun is wearing a spacesuit that can be approximated as perfectly white ( e=0 ) except for a 5 cm × 8 cm patch in the form of the astronaut's national flag. The patch has emissivity 0.300. The spacesuit under the patch is 0.500 cm thick, with a thermal conductivity k 0.0600 W/m , and its inner surface is at a temperature of 20.0 . What is the temperature of the patch, and what is the rate of heat loss through it? Assume the patch is so thin that its outer surface is at the same temperature as the outer surface of the spacesuit under it. Also assume the temperature of outer space is 0 K. You will get an equation that is very hand to solve in closed form, so can solve it numerically with a graphing calculator, with software, or even by trial and error with a calculator.
What are the following temperatures on the Kelvin scale? (a) 68.0 F, an indoor temperature sometimes recommended for energy conservation in winter (b) 134 F, one of the highest atmospheric temperatures ever recorded on Earth (Death Valley, California, 1913) (c) 9890 F, the temperature of the surface of the Sun
The robot HooRU is lost in space, floating around aimlessly, and radiates heat into the depths of the cosmos at the rate of 10.7 W. H0ORU's surface area is 1.67 m? and the emissivity of its surface is 0.227. Ignoring the radiation that HooRU absorbs from the cold universe, what is HooRU's temperature T? T = K
A cube of edge length 6.0 * 10-6 m, emissivity 0.75, and temperature -100C floats in an environment at -150C.What is the cube’s net thermal radiation transfer rate?
A body whose surface area is 0.2 m2, emissivity is 0.8, and temperature is 100°C is placed in a large, evacuated chamber whose walls are at 25°C. What is the rate at which radiation is emitted by the surface, in W? What is the net rate at which radiation is exchanged between the surface and the chamber walls, in W?
An electric kitchen range has a total wall area of 1.40 m2 and is insulated with a layer of fiberglass 4.0 cm thick. The inside surface of the fiberglass has a temperature of 175 degrees C and its outside surface is at 35 degrees C. The fiberglass has a thermal conductivity of 0.040 W/(m*K). What is the heat current through the insulation, assuming it may be treated as a flat slab with an area of 1.40 m2? What electric-power input to the heating element is required to maintain this temperature?
An object has an emissivity of 0.725. At temperature T, it radiates heat at a rate of 10.W. What is its rate of heat radiation at temperature 2T?
Electronics and inhabitants of the International Space Station generate a significant amount of thermal energy that the station must get rid of. The only way that the station can exhaust thermal energy is by radiation, which it does using thin, 1.7 m -by-3.8 m panels that have a working temperature of about 6° C. How much power is radiated from each panel? Assume that the panels are in the shade so that the absorbed radiation will be negligible. Assume that the emissivity of the panels is 1.0. Express your answer with the appropriate units. ► View Available Hint(s) P = μA Value Units ?