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. S

    Q&A: How Does Work & Energy Relate to Solids, Liquids & Gases?

    I can understand how this applies to gases as in that scenario work done = pressure * change in volume and if change in volume is zero then W=0 so change in internal energy = Q. But I do not understand how this applies generally to all types of substances, say solid, liquid and gas.
  2. P

    Programs Can one conduct interdisciplinary work as a biological psych researcher?

    I am a undergraduate in a non clinical psychology with a special focus in evolutionary psychology, human nature, and personality. I will keep it short and sweet: - What restrictions are on me as a biological psychologist compared to that of a biologist in terms of conducting research? - Can I...
  3. Salman Ali

    Can all the multiplexers work for any number of variables given?

    Can all the multiplexers work for any number of variables given? For example can I make a 16:1 multiplexer for 2 variables inputs, A and B?
  4. C

    Why does it not work to carry a laser and shine it on a light sail?

    Reactionless drives are impossible. That means that a laser carried on a satellite would produce no thrust. Why, then, would shining that laser on a light sail not produce a net force? Using a fan to blow air on a sail does not work because the fan and the sail produce opposing forces. But...
  5. Emilyyyyyyyyy

    Calculate the impact force when falling from a height

    To find vx vx = dx/t = 3.86 m/1.5 s= 2.573 m/s To find Ek Ek = ½mvx²= ½(79.4)(2.573)²= 262.8 J W = FnetΔd Fnet = 262.8 J/ 3.86 m = 68 N He hits him with a force of 68N
  6. C

    Work Problem -- Wood Block Sliding into a Spring

    W_net = Integral from 0 to 0.70 meters [ - F_spring - F_friction ] = 1/2 * (-k) * x^2 - mu * mg * normal force * x = 1/2 * (-325N/m) * (.70)^2 - 0.250 * 6kg * 9.81m/s^2 * 0.70 - 0 = - 89.93 Joules Is this correct and am I setting this whole thing up correctly? The negative signs have me...
  7. almostvoid

    Trying to get a pen to work in so little to no gravity in space

    The best story from space I remember is how NASA spent a huge pile of money trying to get a pen to work in so little to no gravity in space. They worked and worked away and the Soviets found the solution: using a pencil.
  8. H

    In a car ignition how does a circuit work?

    As I get it is that after the contact breaker breaks the contact then the current flows from plus of the battery through the primary winding then through the capacitor and to the minus of the battery. But then what happens to the secondary current? It goes from secondary coil and then what? Does...
  9. C

    What is the difference between flow energy and boundary work?

    What is the difference between the two? Also, as another question, for enthalpy, is it correct to define it to be the sum of internal energy and flow energy or is there another understanding for it? Thanks in advance
  10. P

    Physics Going back for a masters, or is work experience just as good

    I am just looking for some opinions. I have been considering going to get my masters in Material Science (I have a B.S. in physics). I currently have a great job in the field, and it teaches me a ton. When getting my masters, I would keep the job, and they would even pay for a lot of it. I can't...
  11. fight_club_alum

    Uniform distribution of charge and work needed

    Homework Statement A charge of +3.0 μC is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25μC from infinity to the centre of the circle? a . 5.4 J b. 3.4 J <- answer c. 4.3 J d. 2.7 J e. 6.8 J=...
  12. M

    How far does the block slide? (work, spring, incline)

    Homework Statement The system is released from rest with no slack in the cable and with the spring stretched 225 mm. Determine the distance s traveled by the 3.2-kg cart before it comes to rest (a) if m approaches zero and (b) if m = 2.5 kg. Assume no mechanical interference and no friction...
  13. R

    Sauna rocks: how do they work?

    I've looked at many posts related to saunas, and all have been about what happens when you pour water on the sauna rocks and so forth so I believe that question has already been answered. I've struggled to find, however, what physical mechanism governs the heating of saunas? Then, more...
  14. A

    What is the work done on cart by the string?

    Homework Statement A cart of mass M1 = 6 kg is attached to a block of mass M2 = 3 kg by a string that passes over a frictionless pulley. The system is initially at rest and the table is frictionless. After the block has fallen a distance h = 1 m: What is the work Ws done on the cart by the...
  15. M

    Need to calculate work -- Lifting and then sliding a box....

    Homework Statement To lift a box it needs 250N force (F). How much work (A) has to be done to lift it at height (h) 1.2m and to slide it horizontaly (l) 1.2m. Coefficient of friction is 0.2 (μ) F = 250N h = 1.2m l = 1.2m μ = 0.2 A = ? on both situations 2. Homework Equations A = F * h A = F *...
  16. solarcat

    Calculating Work for Launching a Spacecraft to a Great Distance from Earth

    Homework Statement Say you're launching a spacecraft of mass m from the surface of the Earth (mass Me and radius re) to a low height h (h is much smaller than r, so h is essentially negligible). How much work is required to move the spaceship from its low orbit to a great distance from earth...
  17. Erik Ayer

    I Can the quantum eraser work without coincidence?

    I understand that downconverted light is not coherent, so that there are essentially many overlapping interference patterns and that coincidence detection filters out one of those patterns. However, could the downconverted light be filtered such that interference can be detected without...
  18. Avatrin

    Job Skills Data Science on Github: How to Get Started Quickly

    Hi I have the educational background to do a few jobs I have seen posted as "data scientist" or "data engineer". However, I keep getting told that to get a job like that with my background, in mathematics, I need to post code examples on Github. However, I always feel like my ideas are either...
  19. M

    Work exchanged by a system, and internal forces' work

    Homework Statement Hi to everyone, I'm studying thermodynamics, especially I'm focused on the work exchanged by a system. Book's explanation says that when the system received a force from the environment [F(e-s)] (on its surface) it reacts with a force from the system to the environment...
  20. solzonmars

    How does a Faraday Cage block electric fields?

    Why does a Faraday Cage work? (or more generally, why does the inside of a conducting shell have no electric field if there are charges placed outside it?) I understand that this is the result of polarisation, but why does the polarisation happen to exactly cancel out the field? Could there be...
  21. Akash47

    Calculating Pump Power for Well Water Removal

    Homework Statement A well has a diameter of 6 m and a height of 15 m.2/3 of volume of the well is filled with water.A pump can vacate 1/3 of volume of water from the well in 7 minutes 20 seconds.What is the power of the pump? Homework Equations W=mgh, P=W/t The Attempt at a Solution The...
  22. solarcat

    Work Done by Gravity and Tension in a Pulley System

    Homework Statement Two blocks are attached to a rope across a pulley. Block A is on the ground and has a mass of 4 kg. Block B is 2 meters above the ground and has a mass of 12 kg. When the blocks are released, block B hits the floor and block A rises to 2 meters; each block has a final speed...
  23. T

    Nuclear Explosion in Space… How would it work?

    Did a quick search of an explosion in a vacuum and got most of what I was looking for, but on CBS Sunday morning they had a segment on restoring and reevaluating all of the immense footage of America's atmospheric nuclear testing program. They showed some amazing footage of the expansion of the...
  24. A

    Work done by Hooke's Law? (Calc 2)

    An open tank has the shape of a right circular cone. The tank is 8 feet across the top and 6 feet high. How much work is done in emptying the tank by pumping the water over the top edge? (The weight-density of water is 62.4 pounds per cubic foot.)
  25. Curtiss Oakley

    Problem involving energy/motion

    Homework Statement A ball of mass m=0.300 kg is connected by a strong massless rod of length L = 0.800 m to a pivot and held in place with the rod vertical. A wind exerts constant force F to the right on the ball as shown below. The ball is released from rest. The wind makes it swing up to...
  26. Isolde Wilde

    DIY Stirling engine project

    hello, I had made an DIY alpha type Stirling engine for my physics project and now I have to write an report about the relationship between the heat given to the engine and the motion of the wheel. I had searched a lot about Stirling engines and I learned about work, energy, efficiency...
  27. E

    How do motors on gimbals work? (2-axis camera mount application)

    Hello everyone, I am trying to build a 2-axis camera gimbal, which will control yaw and pitch. I have bought sensorless BLDC motors (GB280870KV) which I drive using SPWM. For knowing the camera orientation, I am using IMU sensors (accelerometer, gyroscope, and magnetometer) integrated on the...
  28. Romain Nzebele

    How to calculate the work done

    Homework Statement A sledge loaded with bricks has a total mass of 18.0 kg and is pulled at constant speed by a rope inclined at 20.0° above the horizontal. The sledge moves a distance of 20.0 m on a horizontal surface. The coefficient of kinetic friction between the sledge and surface is...
  29. W

    Work Check: Simple entanglement problem

    Homework Statement Could someone assist me in skimming through my work for this problem? Many thanks! I attached an image of the problem below. Also, I only need help for the first part (part a), cheers.Homework Equations General entangled state vector of a two-particle system: $$|\psi...
  30. W

    Work Check: Neutron Scattering

    Homework Statement Hi all, could someone assist me in checking through my work? Many thanks in advance! An image of the problem is attached below (problem 1b) Homework Equations Far field approximation of a scattered wavefunction: $$\psi_s (\vec{r}) \approx \Psi_i \ r^{\frac{1-d}{2} } \...
  31. opus

    Electronics How does this Adruino Code Work?

    Following up on my previous thread, I found a project that I can do for this Arduino. Its really just a little synthesize keyboard thing, but I'm wondering how the code works. Kind of just the logic behind it. I know that some of the stuff at the bottom deals with tones and frequencies and...
  32. H

    The work of magnetic force on the wire

    When the two current carrying wires (with identical current directions) attract each other, it seems that the magnetic field of wires do work while we know that magnetic force is perpendicular to the velocity of charge. I would like to know whether the the two wires get closer or not? What about...
  33. R

    Find suitable SI units to work with a Vibration Sensor

    We are working on an IOT project in which we are trying to learn about different vibrations of using Wireless Vibration Sensor According to the manual, the wireless vibration sensor is giving the output while testing on CNC machine device 0.75, 0.71,0.69 whose SI units are in 'g'(which is...
  34. A

    Work Check - Centripetal force - Finding Tension in a Rope

    Homework Statement A man, with a mass of 85kg, swings from a vine with a length of 11m. If this speed at the bottom of the swing is 8m/s, what is the tension if g = 10m/s^2? Given: m (mass) = 85kg r (radius) = 11m V (speed) = 8m/s g = 10m/s^2 T = ? Homework Equations Fc (centripetal force) = T...
  35. W

    Work Check: Heat transfer between reservoir and small system

    Homework Statement Could someone look through my work? The parts where I wrote (??) are steps I am especially unsure about. Many thanks in advance. A large reservoir at temperature ##T_r## is placed in thermal contact with a small system at temperature ##T##. They end up at temperature...
  36. F

    Do transistors only work with DC and not with AC?

    Hello, I was reading an electronics book which state that transistors work with DC signals only (not AC), suggesting that relays are needed to switch AC signals. Is that a mistake? When used for amplification, I have seen transistors amplifying time-varying signals (which means AC). Unless...
  37. Np14

    Energy Equation for a Roller Coaster on a Full Circular Loop

    Homework Statement What is the energy equation for a roller coaster already in motion from the ground with to the top of a full circular loop = point B in the image. My question is would the car still have kinetic energy at the top of the loop? Homework Equations Kinetic Energy Equation...
  38. J

    B Why the Fourier series doesn't work to solve any differential equation?

    I know this may sound as a stupid question but I would like to clarify this. An arbitrary function f can be expressed in the Fourier base of sines and cosines. My question is, Can this method be used to solve any differential equation? You plug into the unkown function the infinite series and...
  39. K

    Virtual work in Atwood's machine

    The first chapter in Goldstein's Classical Mechanics ends with 3 examples about how to apply Lagrange's eqs. to simple problems. The second example is about the Atwood's machine. The book says that the tension of the rope can be ignored, but I don't understand why. The two masses can move...
  40. T

    How much work is done when a satellite is launched into orbit?

    Homework Statement A Satellite is brought up into a geostationary orbit (altitude 35800km measured from the surface of the earth). Satellite weights 1000.0kg. How much work is required to bring satellite from a surface of the Earth to geostationary orbit? Homework Equations Newton's law of...
  41. jybe

    Thermodynamics: calculating work question

    1. Homework Statement What are the values of q, w, ΔU, ΔH for the following constant pressure process for a system containing 0.596 moles of CH3OH ? CH3OH(g, 123.0 ºC, 1.00 atm) ⟶ CH3OH(l, 30.0 ºC, 1.00 atm)Molar heat capacity for CH3OH(g), Cp,m = 44.1 J K−1 mol−1 Molar heat capacity for...
  42. I

    How long does it take for gravitational effects to work?

    Imagine a ball being tossed into 'the air'. At its peak, the ball has a velocity of 0(m/s), but how long does it actually have this velocity for? --> Neglecting the effects of air-resistance. Obviously the ball undergoes constant 'g' the whole time, but the answer to my question doesn't relate...
  43. D

    Chemistry Volunteer/unpaid work to build skills

    I got a chemistry degree a few years ago bit I didn't use it to get a job since I've been doing other things. I love working in the lab and would really love to build up my skills but I don't see myself getting a paid chemistry job any time soon so looking for another way to gain lab experience...
  44. Burhan Uddin

    Calculating the work done using a line integral

    Homework Statement a) A point charge + q is placed at the origin. By explicitly calculating the relevant line integral, determine how much external work must be done to bring another point charge + q from infinity to the point r2= aŷ ? Consider the difference between external work and work...
  45. S

    I How does magnetism work in QM?

    Electrons' spin state is responsible for magnetism inside a magnet. Two magnets interact at a distance, but what about the space between and around the two magnetic objects? In CM there are field lines and vector fields, but what is actually happening at the QM level?
  46. L

    How do we calculate kinetic and potential energy in physics?

    Hello:) Ok, I am in my thermos class and I ran into a question about work and energy. I figured out the correct answer based off of the formula given. But what MY question is, goes back to physics 1. How are work and Ke related? IE, work is F*d and F is mg. But in Ke, I do not see the g. How...
  47. C

    Calculating the final speed w/ work & friction

    The problem is asking me to find the final speed of a 1100 kg car traveling at 24 m/s through 18m of mud, where the resistive force on the car is 17000 N. I don't actually know how to go about doing this, so any pointers in the right direction would be super helpful.
  48. N

    Exploring Thermodynamic Work: PV, Mechanical, and Non-Mechanical

    In thermodynamics, what is the relationship between the terms, "pressure–volume work", "mechanical work", "non-mechanical work", "∫pdV", and "-∫Vdp"?
  49. jybe

    How Do You Calculate Work When Compressing Gas?

    Homework Statement What is w when a gas is compressed from 42.1 L to 25.1 L using a constant external pressure of 739 Torr? Remember to include a "+" or "−" sign as appropriate. Homework Equations W = -P(dV) The Attempt at a Solution Pressure = (739 Torr / 760 Torr)*(101.325 kPa) W =...
  50. Ben Harris

    Work done on a meteor approaching the Earth -- Is it +ve or -ve?

    Hi all, i am trying to figure out if work done by gravity is positive or negative on an approaching meteor, I have used W(1->2) = integral (1->2) F(gravity) dot dr. and got a result of (GMem/r2) - (GMem/r1). Were G is gravity, Me is Earth mass, m is meteor mass and r1, r2 are initial and...
Back
Top