BIO Radiation from the head is a major source of heat loss from the human body. Model a head as a 20-cm-diameter, 20-cm-tall cylinder with a flat top. If the body’s surface temperature is what is the net rate of heat loss on a chilly day? All skin, regardless of color, is effectively black in the infrared where the radiation occurs, so use an emissivity of 0.95.

BIO Radiation from the head is a major source of heat loss from the human body. Model a head as a 20-cm-diameter, 20-cm-tall cylinder with a flat top. If the body’s surface temperature is what is the net rate of heat loss on a chilly day? All skin, regardless of color, is effectively black in the infrared where the radiation occurs, so use an emissivity of 0.95.

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter11: Energy In Thermal Processes

Section: Chapter Questions

Problem 58AP: The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is...

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The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?
The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?
(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a 1.40m2 surface area? Assume that the animal’s skin temperature is 32.0C, that tile air temperature is 5.00C, and that fur has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?
In 1986, a gargantuan iceberg broke away from the Ross Ice Shelf in Antarctica. It was approximately a rectangle 160 km long, 40.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917kg/m3 ? (b) How much heat transfer (in joules) is needed to melt it? (c) How many years would it take sunlight alone to melt ice this thick, if the ice absorbs an average of 100W/m2, 12.00 h per day?
(a) A firewalker runs across a bed of hot coals without sustaining burns. Calculate the heat transferred by conduction into the sole of one foot of a firewalker given that the bottom of the foot is a 3.00-mm-thick callus with a conductivity at the low end of the range for wood and its density is 300kg/m3. The area of contact is 25.0cm2, the temperature of the coals is 700C, and the time in contact is 1.00 s. (b) What temperature increase is produced in the 25.0cm3 of tissue affected? (c) What effect do you think this will have on the tissue, keeping in mind that a callus is made of dead cells?
In 1986, an enormous iceberg broke away from the Ross Ice Shelf in Antarctica. It was an approximately rectangular prism 160 km long, 40.0 kin wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917 kg/m3? (b) How much heat transfer (in joules) is needed to melt it? (c) How many years would it take sunlight alone to melt ice this thick, if the ice absorbs an average of 100 W/m2, 12.00 h per day?
A glass windowpane in a home is 0.620 cm thick and has dimensions of 1.00 in 2.00 in. On a certain day, the temperature of the interior surface of the glass is 25.0C and the exterior surface temperature is 0C. (a) What is the rate at which energy is transferred by heat through the glass? (b) How much energy is transferred through the window in one day, assuming the temperatures on the surfaces remain constant?
A steel plate has a circular hole drilled in its center. If the diameter of the hole varies according to thermal linear expansion, show that the area of the original circle A0 changes with an increase in temperature T, following the approximate relation A CA0 T, where C = 2. Hint: (T)2T.
(a) Calculate the rate of heat conduction through a double-paned window that has a 150-m2 area and is made of two panes of 0.800 cm-thick glass separated by a 1.00 cm air gap. The inside surface temperature is 15.0 C, while that on the outside is 10.0 OC. (Hint: There are identical temperature drops across the two glass panes. First find these and then the temperature drop across the air gap. This problem ignores the increased heat transfer in the air gap due to convection.) (b) Calculate the rate of heat conduction through a 1.60-cm-thick window of the same area and with the same temperatures. Compare your answer with that for part (a).
(a) An exterior wall of a house is 3 m tall and 10 m wide. It consists of a layer of drywall with an R factor of 0.56, a layer 3.5 inches thick filled with fiberglass batts, and a layer of insulated siding with an R factor of 2.6. The wall is built so well that there are no leaks of air through it. When the inside of the wall is at 22 and the outside is at 2 , what is the rate of heat flow through the wall? (b) More realistically, the 3.5-inch space also contains 2-by-4 studs—wooden boards 1.5 inches by 3.5 inches oriented so that 3.5-inch dimension extends from the drywall to the siding. They are "on 16-inch centers," that is, the centers of the studs ale 16 inches apart. What is the heat current in this situation? Don't worry about one stud mole or less.
(a) At what temperature does water boil at an altitude of 1500 m (about 5000 ft) on a day when atmospheric pressure is 8.59104N/m2 ? (b) What about at an altitude of 3000 m (about 10,000 ft) when atmospheric pressure is 7.00104N/m2 ?
1. a. B kg of water at 50°C is poured into a bucket that contains D kg of ice at 0°C. Find the equilibrium temperature (neglect the influence of the bucket)? b. What is the rate of heat transfer by radiation if a hot tea pot in 100 °C sits outside in temperature B/5 °C. Take the surface area of the pot as B/10 m². The emissivity of pot is D/20 in the infrared, where the radiation takes place. Stephan Boltzmann constant 5.67 × 10-8 W/m²·Kª B:27.0 D:9.0