A block of wood and a block of metal are both put into a freezer overnight. When you take them out, you notice that the block of metal feels colder than the wood. Does this mean that the metal became colder than the wood? No. The metal is a better conductor, so will transfer heat away from your body more quickly than the wood. Yes. Because metal is a conductor, its temperature will become lower than the environment around it. Yes. Metal will always become colder than wood. No. Metal will always take longer than wood to cool down.

A block of wood and a block of metal are both put into a freezer overnight. When you take them out, you notice that the block of metal feels colder than the wood. Does this mean that the metal became colder than the wood? No. The metal is a better conductor, so will transfer heat away from your body more quickly than the wood. Yes. Because metal is a conductor, its temperature will become lower than the environment around it. Yes. Metal will always become colder than wood. No. Metal will always take longer than wood to cool down.

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 95P: (a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I...

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(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?
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.
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.
For the human body, what is the rate of heat transfer by conduction through the body's tissue with the following conditions: the tissue thickness is 3.00 cm, the difference in temperature is 2.00 , and the skin area is 1.50 m2. How does this compare with the average heat transfer rate to the body resulting from an energy intake of about 2400 kcal per day? (No exercise is included.)
When our bodies get too warm, they respond by sweating and increasing blood circulation to the surface to transfer thermal energy away from the core. What effect will those processes have on a person in a 40.0 hot tub?
During heavy exercise, the body pumps 2.00 L of blood per minute to the surface, where it is cooled by 2.00ºC . What is the rate of heat transfer from this forced convection alone, assuming blood has the same specific heat as water and its density is 1050 kg/m? (answer in W)
To help keep his barn warm on cold days, a farmer stores 837 kg of solar-heated water (Lf = 3.35E+5 J/kg) in barrels. For how many hours would a 1.91 kW electric space heater have to operate to provide the same amount of heat as the water does, when it cools from 15.0 to 0 °C and completely freezes?
How many joules of heat transfer are required to thaw a 0.777-kg package of frozen vegetable juice originally at 0°C if its latent heat of fusion is the same as that of water (334 kJ/kg)? J
A high-end gas stove usually has at least one burner rated at 14,000 Btu/h. (a) If you place a 0.50-kg aluminum pot containing 3.0 liters of water at 20°C on this burner, how long will it take to bring the water to a boil, assuming all the heat from the burner goes into the pot? min (b) Once boiling begins, how much time is required to boil all the water out of the pot? min
A 500 W kettle has 1.00 kg of water in it at a temperature of 100° C. How long willit take for the kettle to boil dry?
A thermopane window consists of two glass panes, each 0.50 cm thick, with a 1.0-cm-thick sealed layer of air in between. (a) If the inside surface temperature is 22.1°C and the outside surface temperature is 0.0°C, determine the rate of energy transfer through 1.55 m2 of the window. ?W(b) Compare your answer to (a) with the rate of energy transfer through 1.55 m2 of a single 1.0-cm-thick pane of glass. Disregard surface air layers. (Find the rate of energy transfer.) ?kW
Suppose you stand with one foot on ceramic (k=24 W/mK) flooring and one foot on a wool carpet (k =0.027 W/mK), making contact over an area of 60cm2 with each foot. Both the ceramic and the carpet are 1.4 cm thick and are 8°C on their bottom sides. If the top of the ceramic and carpet at 27°C, calculate the following: a) he rate of heat transfer that occur from the foot kept on wool carpet in watts? b) the rate of heat transfer that occur from the foot kept on ceramic in watts?