A- A grown man holds two metal balls with 5kg of mass in his both hands in one level. He started climbing a stair. Assuming a 20% mechanical efficiency in climbing stairs. In the middle of the stairs there is a fan that blows air with temperature of 25 °C, if the man body temperature is 39 °C, due to action he does. The sweat helped to keep his temperature at constant level. How much does the internal energy decrease when the man mass 65 kg and climbs a 15 m high of stairs? How much thermal energy does the person transfer to the environment as exhaust heat? What does the work the man does if he is climbing in speed of 2 m/s?. Assume the man volume is 0.25 m³.

A- A grown man holds two metal balls with 5kg of mass in his both hands in one level. He started climbing a stair. Assuming a 20% mechanical efficiency in climbing stairs. In the middle of the stairs there is a fan that blows air with temperature of 25 °C, if the man body temperature is 39 °C, due to action he does. The sweat helped to keep his temperature at constant level. How much does the internal energy decrease when the man mass 65 kg and climbs a 15 m high of stairs? How much thermal energy does the person transfer to the environment as exhaust heat? What does the work the man does if he is climbing in speed of 2 m/s?. Assume the man volume is 0.25 m³.

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter21: Heat And The First Law Of Thermodynamics

Section: Chapter Questions

Problem 65PQ

See similar textbooks

Similar questions

(a) Calculate the rate of heat transfer by radiation from a car radiator at 110C into a 50.0C environment, if the radiator has an emissivity of 0.750 and a 1.20m2 surface area. (b) Is this a significant fraction of the heat transfer by an automobile engine? To answer this, assume a horsepower of 200 hp (1.5 kW) and the efficiency of automobile engines as 25%.
(a) An ideal gas expands adiabatically from a volume of 2.0103 m3 to 2.5103 m3. If the initial pressure and temperature 5.0105 Pa and 300 K, respectively, what are the final pressure and temperature of the gas? Use =5/3 for the gas. (b) In an isothermal process, an ideal gas expands from a of 2.0103 m3 to 2.5103 m3. If the initial pressure and temperature were 5.0105 Pa and 300 K, respectively, what are the final pressure and temperature of the gas?
(a) How much heat must be added to raise the temperature of 1.5 mol of air 25.0 to 33.0 at constant volume? Assume air is completely diatomic. (b) Repeat the problem for the same number of moles of xenon, Xe.
(a) What is the change in internal energy for the process represented by the closed path shown below? (b) How much heat is exchanged? (c) If the path is traversed in the opposite direction, how much heat is exchanged?
(a) It is difficult to extinguish a fire on a crude oil tanker, because each liter of crude oil releases 2.80107 J of energy when burned. To illustrate this difficulty, calculate the number of liters of water that must be expended to absorb the energy released by burning 1.00 L of crude oil, if the water's temperature rises from 20.0 C to 100 C, it boils, and the resulting steam's temperature rises to 300 C at constant pressure. (b) Discuss additional complications caused by the fact that crude oil is less dense than water.
From Table 21.1, the specific heat of milk is 3.93 103 J/ (kg K). and the specific heat of water is 4.19 103 J/(kg K). Suppose you wish to make a large mug (0.500 L) of hot chocolate. Each liquid is initially at 5.00C. and you need to raise their temperature to 80.0C. The density of milk is about 1.03 103 kg/m3, and the density of water is 1.00 103 kg/m3. a. How much heat must be transferred in each case? b. If you use a small electric hot plate that puts out 455 W, how long would it take to heat each liquid?
In cold climates, including the northern United States, a house can be built with very large windows facing south to take advantage of solar heating. Sunlight shining in during the daytime is absorbed by the floor, interior walls, and objects in the room, raising their temperature to 38.0C. If the house is well insulated, you may model it as losing energy by heat steadily at the rate 6 000 W on a day in April when the average exterior temperature is 4C and when the conventional heating system is not used at all. During the period between 5:00 p.m. and 7:00 a.m., the temperature of the house drops and a sufficiently large "thermal mass" is required to keep it from dropping too far. The thermal mass can be a large quantity of stone (with specific heat 850 J/kg C) in the floor and the interior walls exposed to sunlight. What mass of stone is required if the temperature is not to drop below 18.0C overnight?
In 1986, a gargantuan iceberg broke away from the Ross Ice Shelf in Antarctica. It was approximately a rectangle 160 km long, 40.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917kg/m3 ? (b) How much heat transfer (in joules) is needed to melt it? (c) How many years would it take sunlight alone to melt ice this thick, if the ice absorbs an average of 100W/m2, 12.00 h per day?
A 3.00-g copper coin at 25.0C drops 50.0 m to the ground. (a) Assuming 60.0% of the change in gravitational potential energy of the coin-Earth system goes into increasing the internal energy of the coin, determine the coins final temperature. (b) Does the result depend on the mass of the coin? Explain.
(a) A cyclical heat engine, operating between temperatures of 450C and 150C produces 4.00 MJ of work on a heat transfer of 5.00 MJ into the engine. How much heat transfer occurs to the environment? (b) What is unreasonable about the engine? (c) Which premise is unreasonable?
Unreasonable Results (a) What is the temperature increase of an 80.0 kg person who consumes 2500 kcal of food in one day with 95.0% of the energy transferred as heat to the body? (b) What is unreasonable about this result? (c) Which premise or assumption is responsible?
(a) What is the eficiency of a cyclical heat engine in which 75.0 kJ of heat transfer occurs to the environment for every 95.0 kJ of heat transfer into the engine? (b) How much work does it produce for 100 kJ of heat transfer into the engine?