What is Work: Definition and 1000 Discussions

In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, it is often represented as the product of force and displacement. A force is said to do positive work if (when applied) it has a component in the direction of the displacement of the point of application. A force does negative work if it has a component opposite to the direction of the displacement at the point of application of the force.
For example, when a ball is held above the ground and then dropped, the work done by the gravitational force on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to the ground (a displacement). When the force F is constant and the angle between the force and the displacement s is θ, then the work done is given by:




W
=
F
s
cos
⁡

θ



{\displaystyle W=Fs\cos {\theta }}
Work is a scalar quantity, so it has only magnitude and no direction. Work transfers energy from one place to another, or one form to another. The SI unit of work is the joule (J), the same unit as for energy.

View More On Wikipedia.org
Recent contents Top users
  1. pokemon123

    Understanding Work with Conservative Forces | Physics

    so the concept of work I've never really understood (even after a year and a half of physics classes rip). What mainly confuses me is when the work done is positive or negative. From what I understand the net work=deltaKE or net work=-PE assuming energy is conserved (so if an external force was...
  2. MathematicalPhysicist

    A Why Do Feynman Rules Successfully Model Particle Interactions?

    I am reading Peskin and Schroeder and finished a few years ago Srednicki. What I don't understand is why do Feynman rules work? They are supposed to represent the diverging integrals that appear in the calculations, i.e momentum integrals, are they supposed to be regarded as a pictorial...
  3. H

    Heat and work when temperature increases by 1 degree

    Homework Statement Kinetic energy per mol is 3/2KTHomework Equations Q = nC##\Delta##T U = Q + W W = -P##\Delta##V The Attempt at a Solution 1) internal energy = 3/2NKT 2) heat needed to increase temperature of 1 mol ideal gas by 1 degree at constant volume? Since constant volume, W = 0 Q =...
  4. F

    The work done by the electric field between two plates

    Homework Statement Homework Equations ##V=Ed## ##ΔU=ΔV Q## The Attempt at a Solution Since the electric field is constant between charged plate conductors , d and the potential difference (ΔV) don't change.So, the potential energy (ΔU) remain the same . The answer is (C). Right ?
  5. H

    Work done for isothermal process in terms of Helmholtz func

    The Helmholtz function differential form for a reversible process is: dF = -SdT - PdV, as for a reversible process δW (by system/here an (ideal) gas) = PdV and dS = δQ/T. Therefore, for a reversible isothermal process, dT = 0 and hence dF = -PdV. Therefore, the work done by the system is W =...
  6. C

    How to work out the reflection point of waves

    Homework Statement When a workman strikes a steel pipeline with a hammer, he generates both longitudinal and transverse waves. The two types of reflected waves return 2.4 s apart. How far away is the reflection point? (For steel, vL = 6.2 km/s, vT = 3.2 km/s). Homework Equations Unknown...
  7. harambe

    B Constant Force: Energy Conservation & Path Independence

    I had an argument with my friend regarding constant forces.He said that work done by constant forces are conservative as we can take the force out of the integral and it doesn't depend on the path .But the fact that this information is not given in my textbook as well as by teachers makes me...
  8. L

    About the total work done loading and unloading (setting down) an object

    The other day I saw this question: "A man carries a suitcase weighing 50kg over his head, and travels a distance of 15m along a horizontal direction. What would be the work done?" My answer was: "Suposse the height of the man is 1.8m. Then, the work done by the man, considering the...
  9. C

    Postdoctoral Work Stress and the Human Cost

    A friend shared this article with me recently and I thought I might post it here for discussion. The Human Cost of the Pressures of Postdoctoral Research While I'm not sure that academic journals are the right venue for such statements, I agree that as a community it's important for us to have...
  10. Hydrous Caperilla

    Thermodynamic Work: Non-Conducting Piston & Cylinder

    Homework Statement A non-conducting piston of mass m and area of cross section A is placed on a non-conducting cylinder. Intial height of piston is h and spring is relaxed with a spring constant k.Then,work done in displacing pistin by heating gas is (x is the displacement of the pistion)...
  11. Fig Neutron

    The Mystery: How Boomerangs Work and Come Back Explained

    What makes a boomerang come back when you through it? My guess is that it has something to do with the shape, I'm just not sure what. I have found three boomerangs the fist one is a typical boomerang that looks kind of like this L., the second one is a disc, and the third one is kind of like a...
  12. doglover9754

    Airplane wings -- How do they work and why do they change shape?

    I just went on a Japan trip. In the airplane, besides throwing up my ball and phone, I was doing a little bit of studying. While the plane was in takeoff, in the middle of flying, and landing, I noticed how the wing positions changed. I already know how takeoff works. It works when the plane...
  13. BlackJ

    Need help on a work problem -- Pushing a shoe box up a ramp

    Homework Statement A constant force (Fa) of magnitude 82.0 N is applied to a 3.00 kg shoe box at an angle of 53.0 degrees, causing the box to move up a frictionless ramp at a constant speed. How much work is done on the box by Fa when the box has moved through a vertical distance h = 0.150 m...
  14. A

    Find the amount of work to move a particle from point A to B

    Homework Statement How much work should be done on a point charge of q=15 nC to bring it from infinity to a distance of 3 cm from a surface of a charged sphere? Diameter of sphere is 15 cm, its surface charge density is 12 microC/cm2 Homework Equations W=deltaU=q*deltaV v=kQ/r...
  15. K

    Given a uniform chain on an incline, find the work done by friction

    Homework Statement A uniform chain of mass 'm' and length 'l' rests on a rough incline (inclination is angle 'Q') with its part hanging vertically. The chain (inclined) starts moving up the incline (and the vertical part moving down) provided the hanging (vertical) part equals to 'n' times...
  16. Pushoam

    Virtual work = 0 implies net torque = 0

    Homework Statement Homework Equations ## \vec \tau = \Sigma \vec r_i \times \vec F_i ## The Attempt at a Solution ## \vec \tau = \Sigma \vec r_i \times \vec F_i ## ## \delta W = \Sigma F_i \delta x_i ## Let's take our Cartesian coordinate system such that the axis of rotation...
  17. A

    How does the transfer of electric forces between two objects work

    Questions 1.) Here, the negative charge from the wool is transferred to the plastic rod. I'm curious as to what determines which object is responsible of transferring their charge to the other object. Like why didn't the plastic rod give its negative charge instead? 2.) If we rub 19 more...
  18. A

    How does a magnet's magnetic field work?

    Now I know that the magnetic field is made of photons iam trying to understand how it creates the attraction of force. I am not sure if its true or not I theorized that the magnet emits photons towards the material for example Iron and it turns one end to positively charged and the other end...
  19. D

    How Does W=VIt Describe Energy in Electrical Circuits?

    Homework Statement I have to explain the equation W=VIt and apply it to a circuit. But I do not undertsand what the equation shows. Homework Equations W=VIt The Attempt at a Solution My rough guess is : work done is equal to the time (t) taken for 1A of current to flow at 1V
  20. The Bill

    How do the nozzles on spray bottles work when misting?

    I looked up misting nozzle design, but the results I found referred to two types of industrial misting nozzles which don't match up to what a spray bottle looks like at all. I tried looking up design elements of spray bottle nozzles specifically, but all I found were details on how the pump...
  21. J

    How does does a DC generator work?

    The way I understand most generators that are used in plants is that they take the heat form combustion or fission and use It to create steam to run a turbine with magnets on it that create AC power over a coil. how could a dc generator work?
  22. ZiHao

    How and Why Peltier Tiles work?

    The thing I knew about Peltier Tiles is that when there is a temperature difference, it generates electricity, and the bigger the tempreature difference, the greater the power you will get. But why it works? Basically, I have partnered with three other friends to participate in a science contest...
  23. J

    Work done by friction on smaller block

    Homework Statement Homework EquationsThe Attempt at a Solution If the two blocks were to move together when the external force of magnitude mg is applied , the acceleration would be mg/3m = g/3 . This acceleration would have to be provided by friction . Value of friction should be mg/3 . But...
  24. binbagsss

    Studying How hard is it to do original work in a summer dissertation

    ..in a taught masters (UK). My undergrad project was a literature review on general relativity The topic of my project this summer (3 months) will be modified theories of gravity & cosmology. How do you go about doing some original work at this level? - would the first step be to identify a...
  25. J

    Gravitation - gravity force, centripetal aceleration, work

    1Problem: Two equal satellite, A and B, of a planet of mass M, describe circular trajectories where the radious are 0,5r and r. We can afirm that: A- The intensity of gravitical force acting on B is half of the gravitical force acting on A; B- The value of centripetal aceleration of A is one...
  26. K

    MHB Multivariable calculus line integral work

    calculate the work done by the force field $F(x,y)=(ye^{xy})i+(1+xe^{xy})j$ by moving a particle along the curve C described by gamma (γ):[0,1] in $R^2$, where gamma (γ)=(2t-1, t²-t)
  27. grandpa2390

    Why won't my Matlab code work?

    Homework Statement I need to write a program in Matlab that accomplishes this graph: I keep getting an error on Line31 Column 161 about unexpected parenthesis. They look balanced to me. If I take one away from either side, I get an error that I am short a parenthesis. I also need to change...
  28. F

    Pumping Water -- Please check my pump system design work

    Hey Folks! Just need a quick sanity check ... Putting in a new 4in well and submersible pump ... trying to wrap my brain around the "physics" of it ... Here is what I ***Think I Know*** : 1) The Energy required to move any given volume of water to ground level can be calculated using M*G*H ...
  29. B

    Change of Temperature from Work in Hydrostatic System

    Hi, I have a little conceptual question. I have an idea about the topic, but I would need to formalize it a little bit. The problem is the following: Imagine the following scenario: You put a little bit of water in a bottle, you assure yourself that everything as at a constant temperature and...
  30. almosthavoc

    Very quick question regarding work and kinetic energy

    Homework Statement The question gave a force applied on a block as well as a distance. It also gave the work done by friction which was negative. The question was to find the change in kinetic energy.Homework Equations Wnet = change in KE The Attempt at a Solution I found the work done by the...
  31. E

    The work of the magnetic force

    Homework Statement We put 2 very long parallel wires on a table, in both of them the current flows at the same direction. As a result, they get closer to each other. Does this create a conflict with the fact that magnetic force does not do work? What is the energy source for the work done on...
  32. M

    Calculating work done by a Carnot engine

    "A Carnot engine operates using a heat source at 500 °C, and a heat sink at room temperature (20 °C). Suppose that as a heat source, you use the combustion of 100 cubic feet of natural gas at room temperature and pressure (e.g. in a fuel cell of some kind). Under ideal conditions, what is the...
  33. grandpa2390

    Is Work Being Done When a Car Travels at Constant Velocity Against Friction?

    According to my professor if you are lifting a book at a constant velocity , work is being done even though the net force is 0... ok A car is traveling down the highway at a constant velocity, is work being done? He says no because the net force is 0 Now the road is not frictionless . I asked...
  34. FlimFlam

    How can I get my Pi 3 to work in a vacuum?

    Im trying to do some data logging, using a raspberry pi 3 would be super easy as it has a built in WiFi and Bluetooth receiver as well as an SD card. However when the vacuum gets to about -30inHg the Pi shuts off and the red light starts flashing as if there is no OS. Temperatures arent crazy...
  35. P

    How Do Levers Work? Explained Simply

    So my last drawing was too confusing so I’ve tried to sketch it as simply as possible to explain. In the first picture a lever in red is prying the two blue parts apart. The Blue parts are fixed. I’m not too good at all this but as I understand it the arm of the lever is twice as long on the...
  36. karush

    MHB 17.7.07 other orders usually work well and are occasionally easier to evaluate

    The integrals we have seen so far suggest that there are preferred orders of integration for cylindricsl coordinates, but other orders usually work well and are occasionally easier to evaluate. Evaluate the integral \begin{align*}\displaystyle dV&=\int_{0}^{2\pi}\int_{0}^{3}\int_{0}^{z/3}r^3...
  37. Grands

    How important is the work done by people who work in finance?

    Hi guys. Due to the reason that I do not have a great knowledge related to finance, I wanted to ask if someone can simply explain me how important is for the society, the work of the people that work in the finance. How their job is useful for the people? Thanks Grands.
  38. JustAStudent

    Work to move electron/proton between the plates of a charged capacitor?

    Homework Statement A charged capacitor consists of two large flat plates, one with positive charge +Q and the other negative charge -Q. An external agent trans an electron from the positive plate to the negative and also transfers a proton from the negative plate to the positive plate. There is...
  39. K

    Lifting an object, kinetic energy, work and forces

    Homework Statement From a physics multiple choice test: "A car is raised to a height of 10 meters. The car is at rest both before and after it has been lifted. The mass of the car is 900 kg. The total work that has been done on the car during the move is" (The right answer is: zero). Wnet...
  40. A

    Understanding Batteries: Anode, Cathode, Electrolyte

    So I understand in a battery that an anode (such as zinc) and a cathode (such as carbon) are separated by an electrolyte. I also understand that the electrons want to flow into the cathode, but can't get to them, so as soon as a conductor connects the two terminals, current can flow. However...
  41. Pushoam

    Work done in a thermodynamic process

    Homework Statement Homework EquationsThe Attempt at a Solution The work done is maximum in the path (3) as the area covered by this path is maximum. Now, dU = dQ + dW, the work done is minimum in the Path (1) , so dQ should be maximum. Hence, the correct options are A and C. Is this correct?
  42. Physics345

    Need someone to help check my work -- Artificial Gravity Report

    Homework Statement 1. Do research to find out what artificial gravity is and how it is related to centripetal motion. Explain how artificial gravity could be created in a weightless environment and give a reason why we would want to do this.Homework Equations None. The Attempt at a Solution...
  43. rishi kesh

    How does an opamp work as non-inverting amplifier

    Homework Statement I am doing a little bit of research about op amps. What i know so far from the book it that op amp have a very large open loop gain. To reduce the gain to desired amount we need resistor which connect output to invering terminal(negative feedback). Homework...
  44. A

    How Batteries Work: An Electrochemical Explanation

    So, I'm a little confused on how batteries work. I understand they convert chemical energy into electrical energy. I also understand that the battery consists of an anode and a cathode with an electolyte in the middle to force the electrons from the chemical reaction to have to follow the wires...
  45. G

    Which Gas Compression Process Requires the Most Work?

    Homework Statement This is a conceptual question. An ideal gas is compressed to half its initial volume by means of several possible processes. Which of the following processes results in the most work done on the gas? a) isothermal b) adiabatic c) isobaric d) The work done is independent of...
  46. M

    Problems in Classic Mechanics -- looking for complex problems to work on

    Can someone please share complex problems interrelated between Kinamatics, Force, Linear Momentum, Work and Energy along with final answers to cross-check.
  47. G

    When is Gravitational Potential Energy Considered in the Work-Energy Theorem?

    When using the work-energy theorem (Wnet=ΔE), when do you take gravitational potential energy into account? Change in energy implies all types of energy involved, but in what cases would PEg be a part of it?
  48. CollinsArg

    Exploring the Relationship between Work and Constant Velocity

    Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume...
  49. doglover9754

    How do sound waves interact when two radios are facing each other?

    So again, I’ve got this analytical question on my mind and it’s been bugging me for a couple weeks now. So my question is, how do sound waves work? I’m talking about if you put two radios facing each other playing different songs. What would happen? Is it if waves match then they just combine...
  50. A

    I Why does this concavity function not work for this polar fun

    For the polar equation 1/[√(sinθcosθ)] I found the slope of the graph by using the chain rule and found that dy/dx=−tan(θ) and the concavity d2y/dx2=2(tanθ)^3/2 This is a pretty messy derivative so I checked it with wolfram alpha and both functions are correct (but feel free to check in case...
Back
Top