A 1.88 -m ( 6 ft 2 in. ) man has a mass of 81 kg,...
A 1.88 -m ( 6 ft 2 in. ) man has a mass of 81 kg, a body surface area of 1.8 m 2 , and a skin temperature of 35.7 ∘ C. Normally, 80 % of the food calories he consumes go to heat; the rest goes to mechanical energy. His emissivity e is 1 because his body radiates almost entirely nonvisible infrared energy, which is not affected by skin pigment. (Careful! His body at 35.7 ∘ C radiates into the environment at 20.0 ∘ C, but the environment also radiates back into his body. The net rate of radiation is P net = P body − P environment . ) To keep his body’s temperature constant, how many food calories should he eat per day if he is in a room at 20.0 ∘ C and he loses heat only through radiation? food calories per day =
Homework Answers
on 15 of 17 > A 1.88-m (6 ft 2 in.) man has a mass of...
on 15 of 17 > A 1.88-m (6 ft 2 in.) man has a mass of 95 kg, a body surface area of 2.1 m², and a skin temperature of 34.5 °C. Normally, 80% of the food calories he consumes go to heat; the rest goes to mechanical energy. His emissivity e is 1 because his body radiates almost entirely nonvisible infrared energy, which is not affected by skin pigment. (Careful! His body at 34.5 °C radiates into the environment...
2. The average person has 1.4 m2 of skin at a skin temperature of roughly 305...
2. The average person has 1.4 m2 of skin at a skin temperature of roughly 305 K (90°F) Consider the average person to be an ideal radiator standing in a room at a temperature of 293 K (68°F) (a) Calculate the power (energy per uni i) radiated by the average person in the form of blackbody radiation; express your answer in erg s-1. What is the person's "wattage"? (1 W = 107 erg s-1) Compare this to a typical incandescent...
How much power (power is the energy per second) is radiated by the person
Radiation of Energy The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation: = aeAT4 where o 5.67x10-8 J/s - m2 K is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates An ideal jet-black (or black body) radiator has e 1,whereas a perfect reflector has...
The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation...
The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation = ceAT4 t where a 5.67x108 J/(s m2. K4) is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates. An ideal jet-black (or black body) radiator has e 1, whereas a perfect reflector has e...
Thank you so much! Part A You have probably seen people jogging in extremely hot weather...
Thank you so much!
Part A You have probably seen people jogging in extremely hot weather and wondered Why" As we shall see, there are good reasons nat to do thisl When jogging strenuously, an average runner of mass 69.0 kg ?nd surface aea 1 84 m2 produces energy at a How much heat per second is produced just by the act ot jogging? rate of up to 1310 W 800 % of which is converted to heat The jogger...
(33%) Problem 3: Warm blooded animals are home otherm that is, they maintain an approximately constant...
(33%) Problem 3: Warm blooded animals are home otherm that is, they maintain an approximately constant body temperature. (For humans it's about 37°C.) When they are in an environment that is below their optimum temperature, they use energy derived from chemical reactions within their bodies to warm them up One of the ways that animals lose energy to their environment is through radiation. Every object emits electromagnetic radiation that depends on its temperature. For very hot objects like the sun,...
(33%) Problem 3: Warm blooded animals are homeothermic that is, they maintain an approximately constant body...
(33%) Problem 3: Warm blooded animals are homeothermic that is, they maintain an approximately constant body temperature. (For humans it's about 37°C.) When they are in an environment that is below their optimum temperature, they use energy derived from chemical reactions within their bodies to warm them up. One of the ways that animals lose energy to their environment is through radiation. Every object emits electromagnetic radiation that depends on its temperature. For very hot objects like the sun, that...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
Thermal question A 60-kg hiker plans to climb Mt Kosciuszko (2228 m) starting from Thredbo (1365m). Assume that she is 25% efficient at converting chemical energy from food into mechanical work,...
Thermal question
A 60-kg hiker plans to climb Mt Kosciuszko (2228 m) starting from Thredbo (1365m). Assume that she is 25% efficient at converting chemical energy from food into mechanical work, and that essentially all the work goes into the vertical climb. (a) (3 marks) With reference to the data above, how many servings of Nutrigrain should she eat to provide enough energy for the climb? (b) (6 marks) Climbing a mountain warms you up, and makes you sweat one...
Please Show alll work. 1.A person’s blood pressure is 120/70 (measured in mmHg). What must the...
Please Show alll work. 1.A person’s blood pressure is 120/70 (measured in mmHg). What must the height of an IV bag be so that blood is not pushed into the IV line by the blood pressure? 2. A graduate student doing an experiment puts 0.150 moles of helium into a cylinder with a moveable piston. The helium is at a pressure of 1.0 atm and a temperature of 30 °C at the beginning of the experiment. They then compress the...
on 15 of 17 > A 1.88-m (6 ft 2 in.) man has a mass of 95 kg, a body surface area of 2.1 m², and a skin temperature of 34.5 °C. Normally, 80% of the food calories he consumes go to heat; the rest goes to mechanical energy. His emissivity e is 1 because his body radiates almost entirely nonvisible infrared energy, which is not affected by skin pigment. (Careful! His body at 34.5 °C radiates into the environment...
2. The average person has 1.4 m2 of skin at a skin temperature of roughly 305 K (90°F) Consider the average person to be an ideal radiator standing in a room at a temperature of 293 K (68°F) (a) Calculate the power (energy per uni i) radiated by the average person in the form of blackbody radiation; express your answer in erg s-1. What is the person's "wattage"? (1 W = 107 erg s-1) Compare this to a typical incandescent...
Radiation of Energy The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation: = aeAT4 where o 5.67x10-8 J/s - m2 K is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates An ideal jet-black (or black body) radiator has e 1,whereas a perfect reflector has...
The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation = ceAT4 t where a 5.67x108 J/(s m2. K4) is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin. The symbol e stands for the emissivity of the object, which is a measure of how well it radiates. An ideal jet-black (or black body) radiator has e 1, whereas a perfect reflector has e...
Thank you so much!
Part A You have probably seen people jogging in extremely hot weather and wondered Why" As we shall see, there are good reasons nat to do thisl When jogging strenuously, an average runner of mass 69.0 kg ?nd surface aea 1 84 m2 produces energy at a How much heat per second is produced just by the act ot jogging? rate of up to 1310 W 800 % of which is converted to heat The jogger...
(33%) Problem 3: Warm blooded animals are home otherm that is, they maintain an approximately constant body temperature. (For humans it's about 37°C.) When they are in an environment that is below their optimum temperature, they use energy derived from chemical reactions within their bodies to warm them up One of the ways that animals lose energy to their environment is through radiation. Every object emits electromagnetic radiation that depends on its temperature. For very hot objects like the sun,...
(33%) Problem 3: Warm blooded animals are homeothermic that is, they maintain an approximately constant body temperature. (For humans it's about 37°C.) When they are in an environment that is below their optimum temperature, they use energy derived from chemical reactions within their bodies to warm them up. One of the ways that animals lose energy to their environment is through radiation. Every object emits electromagnetic radiation that depends on its temperature. For very hot objects like the sun, that...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
Thermal question
A 60-kg hiker plans to climb Mt Kosciuszko (2228 m) starting from Thredbo (1365m). Assume that she is 25% efficient at converting chemical energy from food into mechanical work, and that essentially all the work goes into the vertical climb. (a) (3 marks) With reference to the data above, how many servings of Nutrigrain should she eat to provide enough energy for the climb? (b) (6 marks) Climbing a mountain warms you up, and makes you sweat one...
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