Suppose the skin temperature of a naked person is 35.8 °C when the person is standing inside a room whose temperature is 25.0 °C. The skin area of the individual is 1.73 m². (a) Assuming the emissivity is 0.604, find the net loss of radiant power from the body. (b) Determine the number of food Calories of energy (1 food Calorie= 4186 J) that is lost in 14.5 hours due to the net loss rate obtained in part (a). Metabolic conversion of food into energy replaces this loss.

Suppose the skin temperature of a naked person is 35.8 °C when the person is standing inside a room whose temperature is 25.0 °C. The skin area of the individual is 1.73 m². (a) Assuming the emissivity is 0.604, find the net loss of radiant power from the body. (b) Determine the number of food Calories of energy (1 food Calorie= 4186 J) that is lost in 14.5 hours due to the net loss rate obtained in part (a). Metabolic conversion of food into energy replaces this loss.

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

See similar textbooks

Similar questions

A small electric immersion heater is used to heat 100 g of water for a cup of instant coffee. The heater is labeled “200 watts”. Calculate the time required to bring all this water from 23.0 °C to 100 °C, ignoring any heat losses. Assume specific heat of water is 4.187 J/g-°C.
An engineer is investigating energy loss through windows. The windowpane of interest is 0.450 cm thick, has dimensions of 0.82 m x 1.95 m, and has a thermal conductivity of 0.8 W/(m °C). On a given cold day, the outside temperature is 0°C and the temperature of the interior surface of the glass is 26.0°C. (a) Determine the rate (in W) at which heat energy is transferred through the window. W (b) Determine the amount of energy (in J) transferred through the window in one day, assuming the temperature on the surfaces remains constant.
One half of a kilogram of liquid water at 273 K (0°C) is placed outside on a day when the temperature is 259 K (-14 °C). Assume that the heat is lost from the water only by means of radiation and that the emissivity of the radiating surface is 0.560. Consider two cases: when the surface area of the water is (a) 0.035 m² (as it might be in a cup) and (b) 1.5 m² (as it could be if the water were spilled out to form a thin sheet). For each case, (a) and (b), determine the time it takes the water to freeze into ice at 0 °C. (a) Number (b) Number i Units Units
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 large cylindrical coffee pot in a coffee shop filled with 10.0 kg of hot coffee at temperature T = 95.0 ° C rests on a wooden table. The steel pot has radius r = 8.00 cm and height h = 50.0 cm and an emissivity e = 0.600. See figure. Assume that all heat loss is radiative through the side and top of the pot, given that wood is a relatively poor thermal conductor. The coffee shop ambient temperature T = 20.0 ° C. a) Find the rate at which the coffee losses heat. b) Assuming constant heat loss rate, what is the coffee temperature after 10.0 minutes have elapsed? Cw = 4.19 x 103 J/kg °C, ρw = 1.00 x 103 kg/m3, σ = 5.67 x 10 -8 W/m2 K4
An incandescent light bulb with a surface area of 0.0121 m2 and an emissivity of 0.95 has a surface temperature of 181.9°C. If the temperature of the surroundings are 20.3°C, what is the net rate of radiation heat transfer between the bulb and the surroundings? [round your final answer to one decimal place]? {σ = 5.6704 x 10-8 W/(m2∙K4)}
Assume, the average radiation intake of the planet earth increases by 120 W/m² momentarily. The planet therefore leaves its thermal equilibrium and starts heating up (neglect additional thermal losses). The total weight of the planet is 6 x 1024 kg. Assume, that we have 1.1 x 109 km³ of sea water and the rest of the planet is rock. The heat capacity of sea water is 3.6 kJ/ kg K, the density is 1 t/m³. The heat capacity of rock is 1.1 kJ/ kg K, the density is 2.9 t/m². Take the cross section area of the planet as A = r² with r being 6500 km. How long does it take, until the temperature of the earth has risen by 3°C? Assume, the full mass of the planet is always on the same temperature. Why is the result much lower than you'd expect? Which of the assumptions is not realistic?
Suppose a skier standing in the shade is completely clothed in white (head to foot, including a ski mask), with clothes that have an emissivity of 0.200 and a surface temperature of 9.5°C. The surroundings are at -15.5°C and her surface area is 1.35 m2. find the net rate of heat transfer in watts via radition from the skier. Q/change in t=
A wood stove is used to heat a single room. The stove is cylindrical in shape, with a diameter of 40.0 cm and a length of 55.0 cm, and operates at a temperature of 410°F. (o = 5.6696 x 108 w/m2 . K, 1 Btu = 1054 J.) (a) If the temperature of the room is 70.0°F, determine the amount of radiant energy delivered to the room by the stove each second if the emissivity is 0.950. (b) If the room is a square with walls that are 8.00 ft high and 30.0 ft wide, determine the R-value needed in the walls and ceiling to maintain the inside temperature at 70.0°F if the outside temperature is 32.0°F. Note that we are ignoring any heat conveyed by the stove via convection and any energy lost through the walls (and windows!) via convection or radiation. ft2. oF . h/Btu
Suppose you walk into a sauna that has an ambient temperature of 52.0°C. (a) Calculate the rate of heat transfer in watts to you by radiation given your skin temperature is 37.0°C, the emissivity of skin is 0.98, and the surface area of your body is 1.40 m2. W (b) If all other forms of heat transfer are balanced (the net transfer is zero), at what rate will your body temperature increase in degrees Celsius per minute if your mass is 70 kg? °C/min
A student is trying to decide what to wear. His bedroom is at 20°C. His skin temperature is 35°C. The area of his exposed skin is 1.50 m². People of all races have skin that is dark in the infrared, with emissivity about 0.900. Find the net energy loss from his body by radiation in 10.0 min.