In this problem you will consider the balance of thermal energy radiated and absorbed by a person. Assume that the person is wearing only a skimpy bathing suit of negligible area. As a rough approximation, the area of a human body may be considered to be that of the sides of a cylinder of length L 2.0 m and circumference C= 0.8 m. For the Stefan-Boltzmann constant use o=5.67 x 10-8 W/m2/K. ▼ Part C Now calculate Por, the thermal power absorbed by the person from the thermal radiation field in the room, which is assumed to be at Troom = 20°C. If you do not understand the role played by the emissivities of room and person, be sure to open the hint on that topic. Express the thermal power numerically, giving your answer to the nearest 10 W. View Available Hint(s) Por= Submit Part D —| ΑΣΦΙ Pet= 1 V | ΑΣΦ/ → C 4 GIG Find Poet, the net power radiated by the person when in a room with temperature Troom = 20°C. Express the net radiated power numerically, to the nearest 10 W View Available Hint(s) ? W C P ? W

In this problem you will consider the balance of thermal energy radiated and absorbed by a person. Assume that the person is wearing only a skimpy bathing suit of negligible area. As a rough approximation, the area of a human body may be considered to be that of the sides of a cylinder of length L 2.0 m and circumference C= 0.8 m. For the Stefan-Boltzmann constant use o=5.67 x 10-8 W/m2/K. ▼ Part C Now calculate Por, the thermal power absorbed by the person from the thermal radiation field in the room, which is assumed to be at Troom = 20°C. If you do not understand the role played by the emissivities of room and person, be sure to open the hint on that topic. Express the thermal power numerically, giving your answer to the nearest 10 W. View Available Hint(s) Por= Submit Part D —| ΑΣΦΙ Pet= 1 V | ΑΣΦ/ → C 4 GIG Find Poet, the net power radiated by the person when in a room with temperature Troom = 20°C. Express the net radiated power numerically, to the nearest 10 W View Available Hint(s) ? W C P ? W

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)...

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In this problem you will consider the balance of thermal energy radiated and absorbed by a person. Assume that the person is wearing only a skimpy bathing suit of negligible area. As a rough approximation, the area of a human body may be considered to be that of the sides of a cylinder of length L=2.0mL=2.0m and circumference C=0.8mC=0.8m. For the Stefan-Boltzmann constant use σ=5.67×10−8W/m2/K4σ=5.67×10−8W/m2/K4. If the surface temperature of the skin is taken to be Tbody=30∘CTbody=30∘C, how much thermal power PrbPrbP_rb does the body described in the introduction radiate? Take the emissivity to be e=0.6e=0.6. Express the power radiated into the room by the body numerically, rounded to the nearest 10 W.
The Earth reradiates the energy it receives from the Sun as a black body. We can calculate the effective temperature of the Earth using the Stefan-Boltzmann equation F = sT4 where we solve for the Temperature T. We use for the energy flux the amount of energy absorbed per second Le divided by the Earth's surface area from which the energy is radiated 4pd2 so that the flux is = Le/(4pd2). Here d is the radius of the Earth given above and s is the Stefan-Boltzmann constant. And the effective temperature is:Te4 = (Le/(4pd2))/s = Le/(4spd2) = __________________ K4and taking the square root of Te4 twice in succession we get the effective Temperature Te:Te = [Le/(4spd2)]0.25 = _________________ Kfor the temperature of the effective Earth. What is the temperature in the Celsius scale? __________ C. (Do I need to tell you how to convert from Kelvin to Celsius? If you don't know look it up in your textbook!!)
Problem 2) Consider the following Maxwell Boltzmann distribution of molecular speeds: P(v) = 4( m 27kBT. mp² v²e 2kgT To calculate average values for say f(v) (function of v) one just integrates f(v) with P(v)dv from zero to infinity = P(v)f(v)dv, where signifies average of f(v). Of course, the distribution should be normalized: P(v)dv=1, (is a requirement for any probability distribution). a) Check the last equation. b) Calculate the average of v. c) Calculate the average of v². d) Calculate from c) the RMS value of the speed. e) Calculate the most probable value of v. f) Square the results of b, d and e and rank them from smallest to the largest value.
Near the surface of a certain kind of star, approximately one hydrogen atom per 10 million is in the first excited level (n = 2). Assume that the other atoms are in the n = 1 level. Use this information to estimate the temperature there, assuming that Maxwell-Boltzmann statistics are valid.
A child has a temperature of 101◦F .If her total skin area is 2 m2, find the energyloss per second due to radiation, assuming theemissivity is 1. Assume the room temperatureis 70◦F. The Stephan-Boltzmann constant is5.6696 × 10^−8 W/m2· K4.Answer in units of W.
Question 8. The filament of a light bulb has a surface area 64 mm2. The filament can be considered as a black body at temperature 2500 K emitting radiation like a point source when viewed from far. At night the light bulb is observed from a distance of 100 m. Assume the pupil of the eyes of the observer to be circular with radius 3 mm. Then (Take Stefan-Boltzmann constant = 5.67 x 10-8 Wm-2K-4, Wien's displacement constant = 2.90 x 10-3m-K, Planck's constant = 6.63 x 10-34 Js, speed of light in vacuum = 3.00 ×108 ms-1) a) power radiated by the filament is in the range 642 W to 645 W b) radiated power entering into one eye of the observer is in the range 3.15 x 10-8 W to 3.25 x 10-8 w c) the wavelength corresponding to the maximum intensity of light is 1160 nm d) taking the average wavelength of emitted radiation to be 1740 nm, the total number of photons entering per second into one eye of the observer is in the range 2.75 x 101 to 2.85 x 1011
Problem 7: You place your ear onto a steel railroad track and hear the sound of a distant train through the rails At = 2.6 seconds before you do through the air. The speed of sound in steel is v, 6100 m/s, and and the air temperature is 24.5° C. Find the distance, D, to the train in meters. D= sin() cotan() cos() asin() atan() acotan() cosh() tan() ♫ ( acos() sinh() tanh() cotanh() Degrees O Radians Hints: 2% deduction per hint. Hints remaining: 2 Submit Hint 7 8 4 5 2 0 BACKSPACE EMA + - VO Feedback 9 6 3 HOME END CLEAR I give up! Feedback: 2% deduction per feedback.
What is the root mean square velocity, vrms, for Helium atom (He) at 66oC? Hint: How many amu does an He atom contain? 1 amu = 1.67 x 10-27 kg Boltzman's Constant, k = 1.38 x 10-23 J/K Give your answer in m/s to 4 significant figures (NO DECIMALS)
Prove that the thermal conductivity could also be written as: neKB 3KBT m Where KB denotes the Boltzmann constant and m denotes the electron ng the expression of the electric conductivity o previously established he problem, prove that the Lorentz number is given by: 2 Steam Heat flow T- OT 2 E+ OT dx A dE dx 3 (KBY == { B E Figure 2 T-(17) E C E- 1 dE dx Cand
The filament of a light bulb has a surface area 64 mm2. The filament can be considered as a black body at temperature 2500 K emitting radiation like a point source when viewed from far. At night the light bulb is observed from a distance of 100 m. Assume the pupil of the eyes of the observer to be circular with radius 3 mm. Then (Take Stefan-Boltzmann constant = 5.67 × 10−8 Wm−2K−4, Wien’s displacement constant = 2.90 × 10−3m-K, Planck’s constant = 6.63 × 10−34Js, speed of light in vacuum = 3.00 ×108 ms−1) a) power radiated by the filament is in the range 642 W to 645 W b) radiated power entering into one eye of the observer is in the range 3.15 × 10−8 W to 3.25 × 10−8 W c) the wavelength corresponding to the maximum intensity of light is 1160 nm d) taking the average wavelength of emitted radiation to be 1740 nm, the total number of photons entering per second into one eye of the observer is in the range 2.75 × 1011 to 2.85 × 1011
Show that the most probable speed of the Maxwell-Boltzmann distribution of molecular speeds is given by sqrt(2kT/m) using dny/dv.
Assume that the Maxwell-Boltzmann distribution is valid in a gas of atomic hydrogen. What is the relative number of atoms in the ground state and first excited state at 293 K (room temperature), 5000 K (the temperature at the surface of a star), and 106 K (a temperature in the interior of a star)?