A person eats a dessert that contains 280 Calories. (This "Calorie" unit, with a capital C, is the one used by nutritionists; 1 Calorie = 4186 J.) The skin temperature of this individual is 36°C and that of her environment is 24° C. The emissivity of her skin is 0.75 and its surface area is 1.3 m2. How much time would it take for her to emit a net radiant energy from her body that is equal to the energy contained in this dessert?

A person eats a dessert that contains 280 Calories. (This "Calorie" unit, with a capital C, is the one used by nutritionists; 1 Calorie = 4186 J.) The skin temperature of this individual is 36°C and that of her environment is 24° C. The emissivity of her skin is 0.75 and its surface area is 1.3 m2. How much time would it take for her to emit a net radiant energy from her body that is equal to the energy contained in this dessert?

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter21: Heat And The First Law Of Thermodynamics

Section: Chapter Questions

Problem 71PQ

See similar textbooks

Similar questions

A person is standing outdoors in the shade where the temperature is 21 °C. (a) What is the radiant energy absorbed per second by his head when it is covered with hair? The surface area of the hair (assumed to be flat) is 190 cm2 and its emissivity is 0.84. (b) What would be the radiant energy absorbed per second by the same person if he were bald and the emissivity of his head were 0.56?
A person is standing outdoors in the shade where the temperature is 33 °C. What is the radiant energy absorbed per second by his head when it is covered with hair? The surface area of the hair (assumed to be flat) is 170 cm2 and its emissivity is 0.85.
A person is standing outdoors in the shade where the temperature is 33 °C. The surface area of the hair (assumed to be flat) is 170 cm2 and its emissivity is 0.85. What would be the radiant energy absorbed per second by the same person if he were bald and the emissivity of his head were 0.65?
A common practice for a person with a high fever is to take a bath in cool water. Assuming an 80 kg person is really ill and needs to cool down from 40°C to 37°C. What is the minimum amount of water needed for bathing assuming the water begins at room temperature, 25°C? The specific heat of the body on average is 3470 J/kg°C and water is 4186 J/kg°C. 16.6 kg 212.2 kg 200 kg 19.8 kg
A window has dimensions of 1.6 m by 2.85 m and is made of glass 7.25 mm thick. On a winter day, the outside temperature is 24° C while the inside temperature is a comfortable at 19.5° C. (k of glass =0.195W/m.K) (1.5+1.5+2 = 5marks)Calculate the following:a) the area of the window in square metres Answer for part 1 .b) the temperature gradient (ΔT/Δx)in kelvin/metre Answer for part 2 .c) the rate of heat lost through the window by conduction in watts Answer for part 3 .
What is the rate of heat conduction through the 3.61-cm-thick fur of a large animal having a 1.29~\text{m}^21.29 m2 surface area? Assume that the animal’s skin temperature is 32.0^\circ\text{C}32.0∘C, that the air temperature is -5.00^\circ\text{C}−5.00∘C, and that fur has the same thermal conductivity as air. Select the correct answer 58.4 W 23.2 W 41.3 W 30.4 W 74.0 W
An engineer who is working on the heat transfer analysis of a house in English units needs the convection heat transfer coefficient on the outer surface of the house. But the only value he can find from his handbooks is 22 W/m2·K, which is in SI units. The engineer does not have a direct conversion factor between the two unit systems for the convection heat transfer coefficient. Using the conversion factors between W and Btu/h, m and ft, and °C and °F, express the given convection heat transfer coefficient in Btu/h·ft2·°F.
What is the cost of heating water in a swimming pool of radius 3.5 m and depth 1.3 m from 13 degress celcius to 27 degress Celcius. If the price of energy is $0.08/ KWh. The specific heat of water is 4186 J/Kg/Cdegrees and density of water is 1000 Kg/m^3. (Hint: Volume of cylinder is πr2h) A. $30.25 B. $65.15 C. $95.50 D. $25.25 E. $133
What is the rate of heat transfer by radiation, with an unclothed person standing in a dark room whose ambient temperature is 22.0C. The person has a normal skin temperature of 33.0C and a surface area of 1.50 m2. The emissivity of skin is 0.97 in the infrared, where the radiation takes place.
Consider a flat-plate solar collector placed on the roof of a house. The temperatures at the inner and outer surfaces of the glass cover are measured to be 33°C and 31°C, respectively. The glass cover has a surface area of 2.5 m2, a thickness of 0.6 cm, and a thermal conductivity of 0.7 W/m·K. Heat is lost from the outer surface of the cover by convection and radiation with a convection heat transfer coefficient of 10 W/m2·K and an ambient temperature of 15°C. Determine the fraction of heat lost from the glass cover by radiation.
A cubical piece of heat-shield-tile from the space shuttle measures 0.13 m on a side and has a thermal conductivity of 0.065 J/(s·m·C°). The outer surface of the tile is heated to a temperature of 1070°C, while the inner surface is maintained at a temperature of 24°C. (a) How much heat flows from the outer to the inner surface of the tile in 4.0 minutes? (b) If this amount of heat were transferred to 2.6 liters (2.6 kg) of liquid water, by how many Celsius degrees would the temperature of the water rise?
A rectangular window in a home has a length of 1.5 m and a height of 0.80 m. If the window allows heat to escape from the home at a rate of 2,000 watts, how thick must the window be if the inside temperature of the home is 220 C and the outside temperature is 3.00C? (Assume that the coefficient of thermal conduction of glass is 0.80 W/mK.) a. 7.1 mm b. 124 mm c. 9.1 mm d. 8.1 mm e. 11 mm