PHYSICS FOR SCI.AND ENGR W/WEBASSIGN
10th Edition
ISBN: 9781337888462
Author: SERWAY
Publisher: CENGAGE L
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Chapter 19, Problem 26P
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 19 Solutions
PHYSICS FOR SCI.AND ENGR W/WEBASSIGN
Ch. 19.2 - Prob. 19.1QQCh. 19.3 - Suppose the same process of adding energy to the...Ch. 19.5 - Prob. 19.3QQCh. 19.5 - Characterize the paths in Figure 19.12 as...Ch. 19.6 - Prob. 19.5QQCh. 19 - Prob. 1PCh. 19 - The highest waterfall in the world is the Salto...Ch. 19 - Prob. 3PCh. 19 - The temperature of a silver bar rises by 10.0C...Ch. 19 - You are working in your kitchen preparing lunch...
Ch. 19 - If water with a mass mk at temperature Tk is...Ch. 19 - An aluminum calorimeter with a mass of 100 g...Ch. 19 - An electric drill with a steel drill bit of mass m...Ch. 19 - A 3.00-g copper coin at 25.0C drops 50.0 m to the...Ch. 19 - How much energy is required to change a 40.0-g ice...Ch. 19 - Prob. 11PCh. 19 - A 3.00-g lead bullet at 30.0C is fired at a speed...Ch. 19 - In an insulated vessel, 250 g of ice at 0C is...Ch. 19 - Prob. 14PCh. 19 - One mole of an ideal gas is warmed slowly so that...Ch. 19 - (a) Determine the work done on a gas that expands...Ch. 19 - A thermodynamic system undergoes a process in...Ch. 19 - Why is the following situation impossible? An...Ch. 19 - A 2.00-mol sample of helium gas initially at 300...Ch. 19 - (a) How much work is done on the steam when 1.00...Ch. 19 - A 1.00-kg block of aluminum is warmed at...Ch. 19 - In Figure P19.22, the change in internal energy of...Ch. 19 - A student is trying to decide what to wear. His...Ch. 19 - A concrete slab is 12.0 cm thick and has an area...Ch. 19 - Two lightbulbs have cylindrical filaments much...Ch. 19 - Prob. 26PCh. 19 - (a) Calculate the R-value of a thermal window made...Ch. 19 - Prob. 28PCh. 19 - Gas in a container is at a pressure of 1.50 atm...Ch. 19 - Prob. 30APCh. 19 - You have a particular interest in automobile...Ch. 19 - You are working in a condensed-matter laboratory...Ch. 19 - Prob. 33APCh. 19 - Prob. 34APCh. 19 - Prob. 35APCh. 19 - Prob. 36APCh. 19 - An ice-cube tray is filled with 75.0 g of water....Ch. 19 - Prob. 38APCh. 19 - An iron plate is held against an iron wheel so...Ch. 19 - One mole of an ideal gas is contained in a...Ch. 19 - Prob. 41APCh. 19 - Prob. 42APCh. 19 - Prob. 43APCh. 19 - A student measures the following data in a...Ch. 19 - (a) The inside of a hollow cylinder is maintained...Ch. 19 - A spherical shell has inner radius 3.00 cm and...Ch. 19 - Prob. 47CP
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