What is Energy transfer: Definition and 155 Discussions

In physics, energy is the quantitative property that must be transferred to a body or physical system to perform work on the body, or to heat it. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement in the International System of Units (SI) of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of one metre against a force of one newton.
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature.
Mass and energy are closely related. Due to mass–energy equivalence, any object that has mass when stationary (called rest mass) also has an equivalent amount of energy whose form is called rest energy, and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy. For example, after heating an object, its increase in energy could be measured as a small increase in mass, with a sensitive enough scale.
Living organisms require energy to stay alive, such as the energy humans get from food. Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the Sun and the geothermal energy contained within the earth.

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  1. K

    Thermodynamics problem, help calculate the energy transfer

    Homework Statement A mass of 5 kg of steam is contained within a piston cylinder assembly. The steam undergoes an expansion from its initial state with e1 = 3000 kJ/kg to its final state with e2 = 2500 kJ/kg. During the process there is a heat transfer of 80 kJ to the steam. Also, a paddle...
  2. K

    Help with a thermodynamics problem, calculate energy transfer?

    Homework Statement A mass of 5 kg of steam is contained within a piston cylinder assembly. The steam undergoes an expansion from its initial state with e1 = 3000 kJ/kg to its final state with e2 = 2500 kJ/kg. During the process there is a heat transfer of 80 kJ to the steam. Also, a paddle...
  3. K

    Archived Thermodynamics problem, calculate energy transfer?

    Homework Statement A mass of 5 kg of steam is contained within a piston cylinder assembly. The steam undergoes an expansion from its initial state with e1 = 3000 kJ/kg to its final state with e2 = 2500 kJ/kg. During the process there is a heat transfer of 80 kJ to the steam. Also, a paddle...
  4. L

    Work, power and energy transfer in dynamic engineering systems

    [b]1. Machanical Prinisiples assignment. Homework Equations Hi guys, i am a new member here, and am really looking for some help. My question is: A wheeled truck has a total mass when loaded of 1500 kg and is to be hauled up an incline of 1 in 1o (sine). g= 9.81 m/s2 and the...
  5. O

    What are some ways to improve wireless energy transfer using coil antennas?

    I've found this video on the web: http://www.youtube.com/watch?v=TIhPayFBE9c&feature=related and id like to be able to build one myself. But i don't really know how to start with this nor how it works. -The 8 shaped coil is really 8 shaped or just 2 coils bound together? -how do you make...
  6. P

    Work & Energy Transfer: Comparing Configurations

    Hello, I've been going over work and energy transfer for some upcoming tests, and I got the following question: http://www.dotcore.co.il/conf1.gif If I look at that configuration, the ball is moving down the inclined path in the same direction as the x axis, and there's no movement on the y...
  7. D

    How do EM waves transfer energy?

    I have some basic doubts regarding how the energy is transferred (e.g. transmission of radio waves) as EM waves. As I know, the wave is not anything that can be practically seen in the space, but it is a model that we use to describe how energy is transferred. But if we think practically, how...
  8. T

    What is the Solution to a Problem on Energy Transfer Using Trigonometry?

    [b]1. A Body Aof 5kg is attached to the end of a light supension cord 2m long and is free to swing in a cirular path in a vertical plane . the body A is drawn aside and the suspension cord is held taut at an angle of 30 below the horizontal . a. determine the linear velocity of the weight...
  9. N

    Exploring Energy Transfer: From Kinetic to Sound?

    hello i know that energy can be transferred but cannot be created or destroyed... but how does energy transfer from one to another(eg. kinetic to sound?) does it passes through an unknown medium? 2nd question, since energy cannot be created why does it exist? Thanks
  10. diegzumillo

    Rate of energy transfer: interior/exterior through glass

    Homework Statement The attached image shows the temperature as a function of the distante to a glass window. The window dimensions are given ( 60cm, 60cm, 0.5cm) and the thermal conductivity of the air and glass are, respectively, 1W/(m.K) and 0,025W/(m.K). What is the energy transfer to the...
  11. T

    Energy transfer from x altitude to geosynchrous altitlude

    Homework Statement INTRO TO THE PROBLEM :For a circular orbit around a massive gravitating body, the speed depends on the radius according to the equation V = sqrt (GM/r) ; for elliptical orbits, the speed varies according to the equation v^2 = 2GM([ 1/r - 1/(2a), where r is the distance...
  12. C

    Exploring the Possibilities of Inter-Universe Energy Transfer

    Possible exit points from this universe to another, or maybe collection points for energy to be saved and reassigned elsewhere? Let's say like they gobble up energy creating singularity which will cause a big bang elsewhere or another universe outside of ours?:confused:
  13. M

    String energy transfer from mousetrap to axle of wheels

    Well, we have a Physics project which requires us to build a car and power this using energy provided by a mousetrap. We may not add other energy sources to power the car; we can only use the mousetrap provided to power the car. Homework Equations Now, thinking about strings and...
  14. T

    Elastic Collision of Two Boxes: Kinetic Energy Transfer

    Homework Statement A 5 g box moving to the right at 20 cm/s makes an elastic head on collision with a 10 g box initially at rest. Mass 1 = .005 kg initial Velocity 1 = .2 m/s Mass 2 = .01 kg initial Velocity 2 = 0 m/s a.) what velocity does each box have after the collision? b.) what...
  15. P

    Calculating Energy Transfer for 75kg Boy Sliding Down Hill

    Homework Statement 75 kg boy, starting from rest, slides down a 30 degrees hill htat is 70 m long. He arrives a thet bottom with a speed of 15 m/s. How much thermal energy has been shared btwn the surface of the hill and the seal of his pants Homework Equations d=(vf2-vi2)/2a KE=1/2Mv2...
  16. B

    Neutron-Atom Collision: Energy Transfer

    1. A neutron in a reactor makes an elastic head- on collision with the nucleus of an atom ini- tially at rest. Assume: The mass of the atomic nucleus is about 13.2 the mass of the neutron. What fraction of the neutron’s kinetic en- ergy is transferred to the atomic nucleus?
  17. N

    Sound wave energy transfer to heat water?

    I was just wondering if anyone has any idea on how I would go about working this out. I have performed the experiments at home, placing a container of water on top of a speaker and then playing a high frequency and high dB sound through them, however, I can not find any equations online or in my...
  18. S

    How Much Energy Does Dropping a Hot Copper Cylinder into Water Transfer?

    A 125 g copper bowl contains 235 g of water, both at 20.0°C. A very hot 300 g copper cylinder is dropped into the water, causing the water to boil, with 5.05 g being converted to steam. The final temperature of the system is 100°C. Neglect energy transfers with the environment. How much energy...
  19. J

    Need Help with Thermo Energy Transfer problem

    A 0.2-m-thick plane wall is constructed of concrete. At steady state the energy transfer rate by conduction through a 1-m^2 area of the wall is 0.15 kW. If the temperature distibution is linear through the wall, what is the temperature difference across the wall, in K? i don't even know where...
  20. M

    Is Energy Transfer via Electromagnetic Radiation Considered a Heat Process?

    Hi All, I have a question and hopefully this is the right board for it. First let me explain that I am a Chemist/Biologist, not a Physicist, and haven’t touched even physical chemistry since my degree many, many years ago. However I have recently found myself reading up on my fundamental...
  21. D

    Looking for resources to do with energy transfer.

    in every element energy is used up to link the protons/neutrons together etc. I am looking for a table that shows how the energy required increases as the number of protons/neutrons increases in the nucleus of the elements. i've searched Google quite a while a can't seem to come across...
  22. M

    Spring-based Slingshot energy transfer

    Homework Statement I am working on an AP physics project, and the assignment is to launch a golf ball accurately at close (10 - 15m) and long (50-60m) range. My group and I have decided on a spring based slingshot that will consist of a T shaped launcher with two springs (one on each side of...
  23. M

    Energy Transfer by Work from Steam to Piston - 5kg Steam Expansion

    A 5 kg of steam contained within a piston-cylinder assembly undergoes an expansion from state1, where the specific internal energy is u1 2709.9 kJ/kg,to state 2, where u2 2659.6 kJ/kg. During the process, thereis heat transfer to the steam with a magnitude of 80 kJ. Also, a paddle wheel...
  24. K

    Bulb Energy Transfer: How Does Voltage Affect Filament Breakage?

    Homework Statement An electric bulb is marked 120 V, 40 W. (a) Calculate the current in this bulb when operating on a 120 V supply. (b) Describe 3 different ways in which energy can be transferred from the filament when it is operating normally. (c) If the light bulb is now connected to...
  25. N

    How Does a Clutched Flywheel Transfer Energy in a Buggy System?

    Hi there As part of a group project, we are using a clutched flywheel to power a buggy. The flywheel spins freely on an axel, on which is a fixed disc, which is pressed against the flywheel using a spring. This is the format of a basic disc clutch. Power is dissipated from the flywheel to the...
  26. Z

    Calculating Arrow Speed from Energy Transfer: Archer's Dilemma [SOLVED]

    [SOLVED] energy transfer? Homework Statement An archer puts a 0.27 kg arrow to thebowstring. An average force of 184.5 N ix exerted to draw the string back 1.3m. Assuming no frictional loss, with what speed does the arrow leave the bow? The Attempt at a Solution So i use the equation...
  27. M

    Calculating Kinetic Energy Transfer: 7.0g and 19.0g Coin Collision

    Homework Statement A 7.0 g coin moving to the right at 22.0 cm/s makes an elastic head-on collision with a 19.0 g coin that is initially at rest. After the collision, the 7.0 g coin moves to the left at 12.5 cm/s. Find the amount of kinetic energy transferred to the 19.0 g coin...
  28. B

    Could a 6ft Object Hitting Earth at 99% Light Speed Destroy It?

    Hello guys! Would an object about 6 ft in length and about 180 lbs hitting the Earth at 99% of light speed destroy the Earth? If not, what would it do? Obviously assuming it did not disintegrate due to frictional forces first. Can this be solved by a simple energy transfer equation? Thanks!
  29. I

    Average rate of energy transfer & rate of energy dissipation.

    Homework Statement 1.) A 70kg boy runs as fast as he can up a flight of stairs which has vertical height of 10metres. He achieves this in 8 seconds. Calculate the average rate of energy transfer into gravitational potential energy that must have occured. 2.) A700kg car traveling at 20ms-1...
  30. J

    Energy transfer from cool part to hot part(q38)

    For this question: http://tinyurl.com/3bozr6 the answer is c. Can anybody kindly explain how this is achieve by refrigerator? Because according for what I study so far , the energy is transfer from hot part to cool part...
  31. E

    Power of Energy Transfer: Solving a 3D Vector Problem

    Homework Statement An object moves with a velocity of [4 m/s,-1 m/s, 3 m/s] and is acted on by a force of [-5 N, 0, +5 N]. What is the power of the energy transfer in this interaction? a. -35 W b. -5 W c. 0 d. +5 W e. +35 W Homework Equations p = Fv The...
  32. L

    Energy transfer in electricity conduction

    Hi, I was wondering something. What is the mechanism of energy transport when electricity is conducted through a conductor? The continuity equation requires current to be constant in a circuit, which means the expectation velocity of the electrons in the conduction bands must be constant...
  33. R

    How Do You Calculate the Speed of Water Waves?

    Homework Statement Water waves in a shallow dish are 6.0cm long At one point, the water oscillates up and down at a rate of 4.8 oscillations per second. What is the speed of the water waves? Homework Equations I am basicaly stuck becuse I don't know how to relate the oscillations to the...
  34. T

    Sun energy transfer into a mousetrap car spring

    Homework Statement In six steps, explain how energy was transferred from the sun to your moving mousetrap car. Homework Equations None, I think. The Attempt at a Solution For the most part, I don't have the slightest idea. I do know how the energy transfers to the spring and powers...
  35. P

    Solve Energy Transfer in Refrigeration System

    The problem statement Refrigerant- 134a enters the compressor of a refrigeration system as saturated vapor at 0.14 MPa, and leaves as superheated vapor at 0.8 MPa and 50C at a rate of 0.04 kg/s. Determine the rate of energy transfers by mass into and out of the compressor. Assume the kinetic...
  36. J

    Interpreting Body Wave-Surface Wave Energy Transfer with Vectors & Tensors

    Homework Statement Hi, as part of my final year project I am investigating how rayleigh surface waves are generated by transverse body waves. I've seen how Kolsky derives these waves by slving the wave equation for this type of waveform. My supervisor wants me to describe the energy transfer...
  37. mbrmbrg

    Mechanical Energy Transfer in a Spring System

    Homework Statement Particle A and partidcle B are held together with a compressed spring between them. When they are released, the spring pushes them apart, and they then fly off in opposite directions, free of the spring. The mass of A is 3 times the mass of B, and the energy stored in the...
  38. L

    Ate of energy transfer by sinusoidal waves on a string q

    Q: A two-dimensional water wave spreads in circular wave fonts. Show that the aplitude A at a distance r from the initial disturbance is proportional to \frac{1}{\sqrt{r}}. (Hint: Consider the energy carried by one outward moving ripple.) Comments: Let's consider the energy carried by one...
  39. O

    How Is Energy Transferred in a Refrigeration Compressor System?

    Hi guys i really need some help on this question. Refrigerant 134a enters the compressor of a refrigeration system as saturated vapour at 0.14MPa and leaves as superheated vapour at 0.8MPa and 50 degrees celsius as a rate of 0.04kg/s. The suction area of the compressor is 10cm^2 and the...
  40. 3

    Exploring Wave Motion: Energy Transfer Without Matter Transfer

    Thats a quote from one of my physics texts, but it seems to me to contradict what I've been tought about enrergy and matter thus far, which isn't much i must add. If wave motion can be defined as energy transfer without matter transfer, then doesn't that violate the famous equation? If so...
  41. D

    Is There a Limit to the Speed of Energy Transfer?

    How fast can energy be transfered? Is there a limit to it? Is it the speed of light? Any prove?
  42. P

    Why Does the Resistance Need to Match for Max Energy Transfer?

    I was wondering why "for maximum transfer of energy from an emf device to a resistive load, the resistance of the emf device must equal the resistance of the load"? So far, I don't have any idea. Could someone explain this to me? Thanks in advance.
  43. C

    Rate of energy transfer by conduction through the window?

    A thermal window with an area of 6.00 m2 is constructed of two layers of glass, each 4.00 mm thick and separated from each other by an air space of 3.00 mm. If the inside is at 20.0°C and the outside is at -38.0°C, what is the rate of energy transfer by conduction through the window? i am...
  44. B

    How Much Natural Gas Is Needed to Heat a House to 28°C?

    The average thermal conductivity of the walls (including windows) and roof of a house in Figure P11.32 is 4.8 10-4 kW/m°C, and their average thickness is 20.0 cm. The house is heated with natural gas, with a heat of combustion (energy given off per cubic meter of gas burned) of 9300 kcal/m3...
  45. V

    Heat - Energy Transfer Question

    Hi, one of my homework problems i received was "A water heater can generate 32, 000kJ/h. How much water can it heat from 15 C to 50 C per hour?" I am having trouble figuring out what formula I would use?
  46. Pengwuino

    Nuclear reaction energy transfer

    Ok i have a question that I've been wondering about for a while here... One of my chemistry professors stated to the class that E=mc^2 means that energy is transferred through light, sound, and heat. Now i was under the impression that 1, heat is light... and sound was simply particle...
  47. S

    Relativity and Energy Transfer via Radiation

    Relativity [seems] to tell me that no object, no matter how small, can be considered individually–it must be considered in its relation to the universe as a whole. The energy that appears between objects separated by space would therefore [seem] to be the manifestation of this connection...
  48. A

    Waves and Energy transfer problem ( am desperate)

    Waves and Energy transfer problem (please am desperate) Well, this is the problem that is breaking my head the time needed for a water wave to change from the equilibrium level to the crest is 0.18s a) what fraction of a wavelength is this? b)what is the period of the wave? c)What is the...
  49. P

    Maximum Energy transfer in Compton Effect

    A photon having E = 14.7 keV energy scatters from a free electron inside a metal. What is the maximum energy the electron can gain from the photon? Lamda'-lamda= change in lamda = h/mc (1-cos(theta)) ...having problems figuring out theta ... I know E=hc/lamda so lamda = hc/E ...so...
  50. P

    Kinetic energy transfer problem

    ok i have a problem with a 0.005kg coin that has an initial velocity of 25cm/s that hits a 0.015kg coin that is at rest. atfer the collision the 0.005kg coin has a velocity of -12.5cm/s. What i have to find is the Kinetic energy transferred was. i got the final velocity for the 0.015kg coin...
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