Thermodynamics: An Engineering Approach ( 9th International Edition ) ISBN:9781260092684
9th Edition
ISBN: 9781260048667
Author: Yunus A. Cengel Dr.; Michael A. Boles
Publisher: McGraw-Hill Education
expand_more
expand_more
format_list_bulleted
Concept explainers
Videos
Textbook Question
Chapter 2.8, Problem 108RP
Some engineers have developed a device that provides lighting to rural areas with no access to grid electricity. The device is intended for indoor use. It is driven by gravity, and it works as follows: A bag of rock or sand is raised by human power to a higher location. As the bag descends very slowly, it powers a sprocket-wheel which also rotates slowly. A gear train
Consider a gravity-driven LED bulb that provides 16 lumens of lighting. The device uses a 10-kg sandbag that is raised by human power to a 2-m height. For continuous lighting, the bag needs to be raised every 20 minutes. Using an efficacy of 150 lumens per watt for the LED bulb, determine (a) the velocity of the sandbag as it descends and (b) the overall efficiency of the device.
Expert Solution & Answer
Trending nowThis is a popular solution!
Students have asked these similar questions
The drive is by V-belts from an electric motor running at 1500 r.p.m. A compressor, requiring 75000W is to run at about 500 r.p.m. The diameter of the pulley on the compressor shaft must not be greater than 1.2 meter while the centre distance between the pulleys is limited to 1.85 meter. The belt speed should not exceed 1500 m/min. Determine the number of V-belts required to transmit the power if each belt has a cross-sectional area of 3 cm2, density 1100 kg/m3 and an allowable tensile stress of 3 MPa. The groove angle of the pulley is 50°. The coefficient of friction between the belt and the pulley is 0.3. Calculate also the length required of each belt.
An electric home stove with 3 burners and microwave is used in preparing a meal as
follows. Burner 1: 20 minutes Burner 2: 40 minutes Burner 3: 15 minutes . Microwave: 30
minutes. If each burner is rated at 1.2 kW and the oven at 1.8 kW, and electricity costs 1000
(IQ =Iraqi Dinar) per k Wh, calculate the cost of electricity used in preparing the meal?
A solar pond power plant produced power output at 350 kW and thermal efficiency of 4%.Sketch the schematic diagram of the system and determine the rate of solar energy collected.
Chapter 2 Solutions
Thermodynamics: An Engineering Approach ( 9th International Edition ) ISBN:9781260092684
Ch. 2.8 - What is the difference between the macroscopic and...Ch. 2.8 - What is total energy? Identify the different forms...Ch. 2.8 - List the forms of energy that contribute to the...Ch. 2.8 - How are heat, internal energy, and thermal energy...Ch. 2.8 - What is mechanical energy? How does it differ from...Ch. 2.8 - Portable electric heaters are commonly used to...Ch. 2.8 - Natural gas, which is mostly methane CH4, is a...Ch. 2.8 - Consider the falling of a rock off a cliff into...Ch. 2.8 - Electric power is to be generated by installing a...Ch. 2.8 - The specific kinetic energy of a moving mass is...
Ch. 2.8 - Determine the specific kinetic energy of a mass...Ch. 2.8 - Calculate the total potential energy, in Btu, of...Ch. 2.8 - Determine the specific potential energy, in kJ/kg,...Ch. 2.8 - An object whose mass is 100 kg is located 20 m...Ch. 2.8 - A water jet that leaves a nozzle at 60 m/s at a...Ch. 2.8 - Consider a river flowing toward a lake at an...Ch. 2.8 - At a certain location, wind is blowing steadily at...Ch. 2.8 - What is the caloric theory? When and why was it...Ch. 2.8 - In what forms can energy cross the boundaries of a...Ch. 2.8 - What is an adiabatic process? What is an adiabatic...Ch. 2.8 - When is the energy crossing the boundaries of a...Ch. 2.8 - Consider an automobile traveling at a constant...Ch. 2.8 - A room is heated by an iron that is left plugged...Ch. 2.8 - A room is heated as a result of solar radiation...Ch. 2.8 - A gas in a pistoncylinder device is compressed,...Ch. 2.8 - A small electrical motor produces 5 W of...Ch. 2.8 - A car is accelerated from rest to 85 km/h in 10 s....Ch. 2.8 - A construction crane lifts a prestressed concrete...Ch. 2.8 - Determine the torque applied to the shaft of a car...Ch. 2.8 - A spring whose spring constant is 200 lbf/in has...Ch. 2.8 - How much work, in kJ, can a spring whose spring...Ch. 2.8 - A ski lift has a one-way length of 1 km and a...Ch. 2.8 - The engine of a 1500-kg automobile has a power...Ch. 2.8 - A damaged 1200-kg car is being towed by a truck....Ch. 2.8 - As a spherical ammonia vapor bubble rises in...Ch. 2.8 - A steel rod of 0.5 cm diameter and 10 m length is...Ch. 2.8 - What are the different mechanisms for transferring...Ch. 2.8 - For a cycle, is the net work necessarily zero? For...Ch. 2.8 - On a hot summer day, a student turns his fan on...Ch. 2.8 - Water is being heated in a closed pan on top of a...Ch. 2.8 - An adiabatic closed system is accelerated from 0...Ch. 2.8 - A fan is to accelerate quiescent air to a velocity...Ch. 2.8 - A vertical pistoncylinder device contains water...Ch. 2.8 - At winter design conditions, a house is projected...Ch. 2.8 - A water pump increases the water pressure from 15...Ch. 2.8 - The lighting needs of a storage room are being met...Ch. 2.8 - A university campus has 200 classrooms and 400...Ch. 2.8 - Consider a room that is initially at the outdoor...Ch. 2.8 - An escalator in a shopping center is designed to...Ch. 2.8 - Consider a 2100-kg car cruising at constant speed...Ch. 2.8 - Prob. 51PCh. 2.8 - What is mechanical efficiency? What does a...Ch. 2.8 - How is the combined pumpmotor efficiency of a pump...Ch. 2.8 - Can the combined turbinegenerator efficiency be...Ch. 2.8 - Consider a 2.4-kW hooded electric open burner in...Ch. 2.8 - The steam requirements of a manufacturing facility...Ch. 2.8 - Reconsider Prob. 256E. Using appropriate software,...Ch. 2.8 - A 75-hp (shaft output) motor that has an...Ch. 2.8 - Prob. 59PCh. 2.8 - An exercise room has six weight-lifting machines...Ch. 2.8 - A room is cooled by circulating chilled water...Ch. 2.8 - The water in a large lake is to be used to...Ch. 2.8 - A 7-hp (shaft) pump is used to raise water to an...Ch. 2.8 - A geothermal pump is used to pump brine whose...Ch. 2.8 - At a certain location, wind is blowing steadily at...Ch. 2.8 - Reconsider Prob. 265. Using appropriate software,...Ch. 2.8 - Water is pumped from a lower reservoir to a higher...Ch. 2.8 - An 80-percent-efficient pump with a power input of...Ch. 2.8 - Water is pumped from a lake to a storage tank 15 m...Ch. 2.8 - Large wind turbines with a power capacity of 8 MW...Ch. 2.8 - A hydraulic turbine has 85 m of elevation...Ch. 2.8 - The water behind Hoover Dam in Nevada is 206 m...Ch. 2.8 - An oil pump is drawing 44 kW of electric power...Ch. 2.8 - A wind turbine is rotating at 15 rpm under steady...Ch. 2.8 - How does energy conversion affect the environment?...Ch. 2.8 - What is acid rain? Why is it called a rain? How do...Ch. 2.8 - Why is carbon monoxide a dangerous air pollutant?...Ch. 2.8 - What is the greenhouse effect? How does the excess...Ch. 2.8 - What is smog? What does it consist of? How does...Ch. 2.8 - Consider a household that uses 14,000 kWh of...Ch. 2.8 - When a hydrocarbon fuel is burned, almost all of...Ch. 2.8 - Prob. 82PCh. 2.8 - A typical car driven 20,000 km a year emits to the...Ch. 2.8 - Prob. 84PCh. 2.8 - What are the mechanisms of heat transfer?Ch. 2.8 - Which is a better heat conductor, diamond or...Ch. 2.8 - How does forced convection differ from natural...Ch. 2.8 - What is a blackbody? How do real bodies differ...Ch. 2.8 - Define emissivity and absorptivity. What is...Ch. 2.8 - Does any of the energy of the sun reach the earth...Ch. 2.8 - The inner and outer surfaces of a 5-m 6-m brick...Ch. 2.8 - The inner and outer surfaces of a 0.5-cm-thick 2-m...Ch. 2.8 - Reconsider Prob. 292. Using appropriate software,...Ch. 2.8 - Prob. 94PCh. 2.8 - Prob. 95PCh. 2.8 - Prob. 96PCh. 2.8 - Prob. 97PCh. 2.8 - For heat transfer purposes, a standing man can be...Ch. 2.8 - Prob. 99PCh. 2.8 - Prob. 100PCh. 2.8 - A 1000-W iron is left on the ironing board with...Ch. 2.8 - A 7-cm-external-diameter, 18-m-long hot-water pipe...Ch. 2.8 - A thin metal plate is insulated on the back and...Ch. 2.8 - Reconsider Prob. 2103. Using appropriate software,...Ch. 2.8 - The outer surface of a spacecraft in space has an...Ch. 2.8 - Prob. 106PCh. 2.8 - A hollow spherical iron container whose outer...Ch. 2.8 - Some engineers have developed a device that...Ch. 2.8 - Consider a classroom for 55 students and one...Ch. 2.8 - Consider a homeowner who is replacing his...Ch. 2.8 - Prob. 111RPCh. 2.8 - The U.S. Department of Energy estimates that...Ch. 2.8 - A typical household pays about 1200 a year on...Ch. 2.8 - Prob. 114RPCh. 2.8 - Prob. 115RPCh. 2.8 - Prob. 116RPCh. 2.8 - Consider a TV set that consumes 120 W of electric...Ch. 2.8 - Water is pumped from a 200-ft-deep well into a...Ch. 2.8 - Consider a vertical elevator whose cabin has a...Ch. 2.8 - Prob. 120RPCh. 2.8 - In a hydroelectric power plant, 65 m3/s of water...Ch. 2.8 - The demand for electric power is usually much...Ch. 2.8 - The pump of a water distribution system is powered...Ch. 2.8 - Prob. 124RPCh. 2.8 - A 2-kW electric resistance heater in a room is...Ch. 2.8 - Prob. 126FEPCh. 2.8 - A 75-hp compressor in a facility that operates at...Ch. 2.8 - On a hot summer day, the air in a well-sealed room...Ch. 2.8 - A fan is to accelerate quiescent air to a velocity...Ch. 2.8 - A 900-kg car cruising at a constant speed of 60...Ch. 2.8 - Prob. 131FEPCh. 2.8 - Prob. 132FEPCh. 2.8 - A 2-kW pump is used to pump kerosene ( = 0.820...Ch. 2.8 - Prob. 134FEPCh. 2.8 - Prob. 135FEPCh. 2.8 - Prob. 136FEPCh. 2.8 - Prob. 137FEPCh. 2.8 - Heat is transferred steadily through a...Ch. 2.8 - The roof of an electrically heated house is 7 m...
Additional Engineering Textbook Solutions
Find more solutions based on key concepts
What types of polymers are most commonly blow molded?
DeGarmo's Materials and Processes in Manufacturing
A windowmounted air conditioner removes 3.5kJ from the inside of a home using 1.75 kJ work input. How much ener...
EBK FUNDAMENTALS OF THERMODYNAMICS, ENH
The moment of inertia Iy for the slender rod in terms of the rod’s total mass m .
Engineering Mechanics: Statics & Dynamics (14th Edition)
Consider a subsonic compressible flow in cartesian coordinates where the velocity potential is given by (x,y)=V...
Fundamentals of Aerodynamics
Select a mechanical component from Part 3 of this book (roller bearings, springs, etc.), go to the Internet, an...
Shigley's Mechanical Engineering Design (McGraw-Hill Series in Mechanical Engineering)
17–1C A high-speed aircraft is cruising in still air. How does the temperature of air at the nose of the aircra...
Thermodynamics: An Engineering Approach
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- An electric motor drives a compressor by use of V-belt. The pulley diameter of the compressor shaft is 1.1 meter while the pulley diameter of the motor shaft is 0.6 meter. The belt speed runs at 27 m/s. The center distance between pulleys is 1.75 m. The groove angle of the pulleys is 35º. Determine the power generated in kW if the tension at the tight side of the belt is 670.5 N. The coefficient of friction between the belt and the pulley is 0.23.arrow_forwardNonearrow_forwardTwo parallel shafts whose centers are 10 meters apart are connected by an open belt drive with a V-belt with a groove angle of 30°. The diameter of the larger pulley is 1000 mm and that of the smaller pulley is 400 mm. The smaller pulley is running at 1000 rpm to deliver 10 kW of power. The mass of the belt is 1 kg/m. Taking centrifugal tension into account, determine the minimal cross-sectional area if the allowable tensile stress of the belt is 5 MPa. The coefficient of friction between the belt and the pulleys is 0.25.arrow_forward
- A heat pump used for heating shown is essentially an air conditioner installed backward. It extracts energy from colder air outside and deposits it in a warmer room. Suppose the ratio of the actual energy entering the room to the work done by the device’s motor is 10.0% of the theoretical maximum ratio. Determine the energy entering the room per joule of work done by the motor given that the inside temperature is 20.0°C and the outside temperature is -5.00°C.arrow_forwardExplain the essential factors that influence the choice of site for a hydro-electric plantarrow_forwardAssume that the average solar insolation in Jamaica is 6500Wh/m² per day and its land area is 10,992 km². Consider that 3% of the land area could be covered by photovoltaic (PV) solar farms and 80% of the area of the solar farm is covered with PV modules with a conversion efficiency of 20%. In this case how much energy expressed in kWh/day could be produced using PV farms? Part B With the aid of diagrams, explain the similarities and differences between a fuel fired steam plant and a combined cycle gas plant. Label all major sections of your diagrams. With the aid of a simple sketch, explain how the following angles affect the location of the sun relative to the earth's sky. • Solar declination Solar azimuth Altitude 1arrow_forward
- An air-cooled window DX unit is used for space cooling. The unit has a capacity of 4.5 tons and has a SEER of 15. If the unit operates for 2204 hours during the summer, how many kWh of electricity will be used? Hint: In the U.S., the SEER is the ratio of cooling in British thermal units (BTUs) to the electrical energy consumed in watt-hours. You may need to convert the unit in this process.arrow_forwardOman has wide expanses/areas of Desert Land which is usually ideal to be used for facilities of Solar Energy for Electrical Power Production. Please write down your own opinions regarding the feasibility of putting up this type of power production installation or facility in Oman.arrow_forwardWhat is the payback time on a solar hot-water system that cost$ 5,000? Assume the system reduces electrical energy consumption by 4,000 kWhr each year and ilectricity costs 16 cents per kWhr. O 8 years O 4 years O 12 years O 15 years.arrow_forward
- A cycle has a qin=350Btu/lbm, and a thermal efficiency of 74%. In this case, the network produced by the cycle is most likely: 320 Btu/lbm 90 Btu/lbm 260 Btu/lbm 350 Btu/lbmarrow_forwardA-Classify the hydro-power stations according to the height of the water, then calculate the height of the water needed to generate 2.86×10 Kw/h if the efficiency is 80% and the volume of water is 5x10⁹ m3, let that mass of Im of water is 1000 kg)arrow_forwardA photovoltaic system is installed. It is determined that the capacity factor of the installation is 21% over the course of a year. In that year it produced 7.73 MWh. What is the size of the installation (based upon a 365-day year)?arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University Press
Mechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSON
Thermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEY
Mechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage Learning
Engineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY
Elements Of Electromagnetics
Mechanical Engineering
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Oxford University Press
Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:9780134319650
Author:Russell C. Hibbeler
Publisher:PEARSON
Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:9781259822674
Author:Yunus A. Cengel Dr., Michael A. Boles
Publisher:McGraw-Hill Education
Control Systems Engineering
Mechanical Engineering
ISBN:9781118170519
Author:Norman S. Nise
Publisher:WILEY
Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:9781337093347
Author:Barry J. Goodno, James M. Gere
Publisher:Cengage Learning
Engineering Mechanics: Statics
Mechanical Engineering
ISBN:9781118807330
Author:James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:WILEY
Work, Energy, and Power: Crash Course Physics #9; Author: CrashCourse;https://www.youtube.com/watch?v=w4QFJb9a8vo;License: Standard YouTube License, CC-BY
Different Forms Of Energy | Physics; Author: Manocha Academy;https://www.youtube.com/watch?v=XiNx7YBnM-s;License: Standard Youtube License