Physics for Scientists and Engineers, Technology Update (No access codes included)
9th Edition
ISBN: 9781305116399
Author: Raymond A. Serway, John W. Jewett
Publisher: Cengage Learning
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Chapter 20, Problem 20.50P
To determine
The reason for the necessity of blood flow to cool the man’s body by calculating the rate of energy conduction in kcal / h
through the tissue layer under skin.
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The rate at which a resting person converts food energy is called one’s basal metabolic rate (BMR). Assume that the resulting internal energy leaves a person’s body by radiation and convection of dry air. When you jog, most of the food energy you burn above your BMR becomes internalenergy that would raise your body temperature if it were not eliminated. Assume that evaporation of perspiration is the mechanism for eliminating this energy. Suppose a person is jogging for “maximum fat burning,” converting food energy at the rate 400 kcal/h above his BMR, and putting out energy by work at the rate 60.0 W. Assume that the heat of evaporation of water at body temperature is equal to its heat of vaporization at 100°C. (a) Determine the hourly rate at which water must evaporate from his skin. (b) When you metabolize fat, the hydrogen atoms in the fat molecule are transferred to oxygen to form water. Assume that metabolism of 1.00 g of fat generates 9.00 kcal of energy and produces 1.00 g of…
A person's basal metabolic rate (BMR) is the rate at which energy is expended while resting in a neutrally temperate environment. A typical BMR is 7.22 x 10° J/day. Convert this
BMR to units of watts and kilocalories (or Calories) per hour.
HINT
(a) watts
W
(b) kilocalories per hour
kcal/h
(c)
Suppose a 1.00 kg object's gravitation potential energy is increased at a rate equal to this typical BMR. Find the rate of change of the object's height in m/s. (The
acceleration of gravity is g = 9.80 m/s2.)
m/s
Overall, 80% of the energy used by the body must be eliminated as excess thermal energy and needs to be dissipated. The mechanisms of elimination are radiation, evaporation of sweat (2,430 kJ/kg), evaporation from the lungs (38 kJ/h), conduction, and convection.A person working out in a gym has a metabolic rate of 2,500 kJ/h. His body temperature is 37°C, and the outside temperature 26°C. Assume the skin has an area of 2.0 m2 and emissivity of 0.97. (σ = 5.6696 10-8 W/m2 · K4)
(a) At what rate is his excess thermal energy dissipated by radiation? (Enter your answer to at least one decimal place.) W(b) If he eliminates 0.44 kg of perspiration during that hour, at what rate is thermal energy dissipated by evaporation of sweat? (Enter your answer to at least one decimal place.) W(c) At what rate is energy eliminated by evaporation from the lungs? (Enter your answer to at least one decimal place.) W(d) At what rate must the remaining excess energy be eliminated through conduction and…
Chapter 20 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
Ch. 20 - Prob. 20.1QQCh. 20 - Suppose the same process of adding energy to the...Ch. 20 - Prob. 20.3QQCh. 20 - Characterize the paths in Figure 19.12 as...Ch. 20 - Prob. 20.5QQCh. 20 - An ideal gas is compressed to half its initial...Ch. 20 - A poker is a stiff, nonflammable rod used to push...Ch. 20 - Assume you are measuring the specific heat of a...Ch. 20 - Prob. 20.4OQCh. 20 - Prob. 20.5OQ
Ch. 20 - Ethyl alcohol has about one-half the specific heat...Ch. 20 - The specific heat of substance A is greater than...Ch. 20 - Beryllium has roughly one-half the specific heat...Ch. 20 - Prob. 20.9OQCh. 20 - A 100-g piece of copper, initially at 95.0C, is...Ch. 20 - Prob. 20.11OQCh. 20 - If a gas is compressed isothermally, which of the...Ch. 20 - Prob. 20.13OQCh. 20 - If a gas undergoes an isobaric process, which of...Ch. 20 - Prob. 20.15OQCh. 20 - Prob. 20.1CQCh. 20 - You need to pick up a very hot cooking pot in your...Ch. 20 - Prob. 20.3CQCh. 20 - Prob. 20.4CQCh. 20 - Prob. 20.5CQCh. 20 - In 1801, Humphry Davy rubbed together pieces of...Ch. 20 - Prob. 20.7CQCh. 20 - Prob. 20.8CQCh. 20 - Prob. 20.9CQCh. 20 - When camping in a canyon on a still night, a...Ch. 20 - Pioneers stored fruits and vegetables in...Ch. 20 - Prob. 20.12CQCh. 20 - Prob. 20.1PCh. 20 - Consider Joules apparatus described in Figure...Ch. 20 - Prob. 20.3PCh. 20 - The highest waterfall in the world is the Salto...Ch. 20 - What mass of water at 25.0C must be allowed to...Ch. 20 - The temperature of a silver bar rises by 10.0C...Ch. 20 - In cold climates, including the northern United...Ch. 20 - A 50.0-g sample of copper is at 25.0C. If 1 200 J...Ch. 20 - An aluminum cup of mass 200 g contains 800 g of...Ch. 20 - If water with a mass mk at temperature Tk is...Ch. 20 - A 1.50-kg iron horseshoe initially at 600C is...Ch. 20 - An electric drill with a steel drill bit of mass m...Ch. 20 - An aluminum calorimeter with a mass of 100 g...Ch. 20 - A 3.00-g copper coin at 25.0C drops 50.0 m to the...Ch. 20 - Two thermally insulated vessels are connected by a...Ch. 20 - A 50.0-g copper calorimeter contains 250 g of...Ch. 20 - Prob. 20.17PCh. 20 - How much energy is required to change a 40.0-g ice...Ch. 20 - A 75.0-g ice cube at 0C is placed in 825 g of...Ch. 20 - A 3.00-g lead bullet at 30.0C is fired at a speed...Ch. 20 - Steam at 100C is added to ice at 0C. (a) Find the...Ch. 20 - A 1.00-kg Mock of copper at 20.0C is dropped into...Ch. 20 - In an insulated vessel, 250 g of ice at 0C is...Ch. 20 - Prob. 20.24PCh. 20 - An ideal gas is enclosed in a cylinder with a...Ch. 20 - Prob. 20.26PCh. 20 - One mole of an ideal gas is warmed slowly so that...Ch. 20 - (a) Determine the work done on a gas that expands...Ch. 20 - An ideal gas is taken through a quasi-static...Ch. 20 - A gas is taken through the cyclic process...Ch. 20 - Consider the cyclic process depicted in Figure...Ch. 20 - Why is the following situation impossible? An...Ch. 20 - A thermodynamic system undergoes a process in...Ch. 20 - A sample of an ideal gas goes through the process...Ch. 20 - A 2.00-mol sample of helium gas initially at 300...Ch. 20 - (a) How much work is done on the steam when 1.00...Ch. 20 - Prob. 20.37PCh. 20 - One mole of an ideal gas does 3 000 J of work on...Ch. 20 - A 1.00-kg block of aluminum is warmed at...Ch. 20 - In Figure P19.22, the change in internal energy of...Ch. 20 - An ideal gas initially at Pi, Vi, and Ti is taken...Ch. 20 - An ideal gas initially at Pi, Vi, and Ti is taken...Ch. 20 - A glass windowpane in a home is 0.620 cm thick and...Ch. 20 - A concrete slab is 12.0 cm thick and has an area...Ch. 20 - A student is trying to decide what to wear. His...Ch. 20 - The surface of the Sun has a temperature of about...Ch. 20 - The tungsten filament of a certain 100-W lightbulb...Ch. 20 - At high noon, the Sun delivers 1 000 W to each...Ch. 20 - Two lightbulbs have cylindrical filaments much...Ch. 20 - Prob. 20.50PCh. 20 - A copper rod and an aluminum rod of equal diameter...Ch. 20 - A box with a total surface area of 1.20 m2 and a...Ch. 20 - (a) Calculate the R-value of a thermal window made...Ch. 20 - At our distance from the Sun, the intensity of...Ch. 20 - A bar of gold (Au) is in thermal contact with a...Ch. 20 - Prob. 20.56PCh. 20 - Prob. 20.57PCh. 20 - A gas expands from I to Fin Figure P20.58 (page...Ch. 20 - Gas in a container is at a pressure of 1.50 atm...Ch. 20 - Liquid nitrogen has a boiling point of 77.3 K and...Ch. 20 - An aluminum rod 0.500 m in length and with a cross...Ch. 20 - Prob. 20.62APCh. 20 - Prob. 20.63APCh. 20 - Prob. 20.64APCh. 20 - Prob. 20.65APCh. 20 - An ice-cube tray is filled with 75.0 g of water....Ch. 20 - On a cold winter day. you buy roasted chestnuts...Ch. 20 - Prob. 20.68APCh. 20 - An iron plate is held against an iron wheel so...Ch. 20 - Prob. 20.70APCh. 20 - A 40.0-g ice cube floats in 200 g of water in a...Ch. 20 - One mole of an ideal gas is contained in a...Ch. 20 - Review. A 670-kg meteoroid happens to be composed...Ch. 20 - Prob. 20.74APCh. 20 - Prob. 20.75APCh. 20 - Prob. 20.76APCh. 20 - Water in an electric teakettle is boiling. The...Ch. 20 - Prob. 20.78APCh. 20 - Prob. 20.79APCh. 20 - A student measures the following data in a...Ch. 20 - Consider the piston cylinder apparatus shown in...Ch. 20 - A spherical shell has inner radius 3.00 cm and...Ch. 20 - Prob. 20.83CPCh. 20 - (a) The inside of a hollow cylinder is maintained...
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