What is Work done: 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.

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  1. Y

    Calculating Work Done for Constant Force Acting on an Object in Space

    1. The problem statement, all variables and given/known A constant Force= <2,4,1> (in Newtons) moves an object in space from (0,0,0) to (2,4,5) ( distance is measured in meters) Calculate the Work done. 2. Homework Equations W= || proj of F onto pq|| ||PQ|| W= F• vector PQ 3. The Attempt...
  2. E

    Work done by doubling the magnetization of a rod

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  3. Uriel

    Work done by a expanding and contracting wire over a Carnot cycle

    Homework Statement Basically I have the following problem. Given the equation of state \sigma = \frac{b}{T}\frac{L - L_0}{L_0} where b and L_0 are positive constants, calculate the work done over a Carnot cycle by a wire with this equation of state.Homework EquationsI already have the work...
  4. E

    The work done by a perfect gas

    Homework Statement An ideal gas at initial temperature T1 and pressure P1 is compressed by a piston to half its original volume. The temperature is varied so that the relation P=AV always holds and A is a constant. What is the work done n the gas in terms of n (moles of gas) R (gas constant)...
  5. T

    Simple doubt in work done by gas

    In First law of thermodynamics , work done by the gas is given by pΔV . I have few doubts regarding this- 1)Is 'p' ,pressure of the gas or external pressure of the surroundings ?If gas is expanding then surely gas pressure should be more than that of the surroundings and vica versa ...
  6. Saitama

    Electrostatics - finding the work done

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  7. P

    Entropy & Work Done: Understanding Reversible Heating/Stirring

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  8. F

    Help finding the work done given 3 different distances?

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  9. C

    Work done by electric force on a point charge in a cylinder?

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  10. T

    Understanding Mechanical Work: Ideal Gas and Fixed Pressure

    Hi all, I was wondering if I am having a definition problem on mechanical work. Since dW = -PdV (as I was told in class), is it correct to say the pressure is fixed with W = -PV, since dW = d(PV) = -VdP - PdV = -PdV suggests dP = 0? Thanks S.
  11. N

    Work done by gravitational force

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  12. M

    Calculating Work in an Expanding Gas: Isobaric vs. Isothermal Processes

    Today in an engineering thermodynamics lecture, the professor gave an example of a gas doing work. We had a cylinder full of helium at a pressure of something like 200kPa absolute and the valve was opened so that the gas would flow out against the atmospheric pressure until the pressures were...
  13. U

    Calculating work done in this thermodynamic cycle

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  14. D

    Work done in climbing the hill

    Suppose a man is climbing up a hill at angle 30 degree from the ground. The mass of the man is 50Kg and he climbs up the hill at uniform acceleration of 2m/s2. What is the work done in climbing up the hill and if he climbs down the hill at the same 30 degree angle with uniform acceleration of...
  15. B

    Work done on accelerating car is zero?

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  16. M

    Solve for Pump Horsepower in 1-Inch Tube with No Heat Transfer

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  17. A

    Calculating Work Done by Upward Buoyant Force on Hot Air Balloon

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  18. K

    Thermodynamics- Work done- Adiabatic process

    I have a small doubt regarding the workdone derivation in adiabatic process. Here is the derivation W= (P1V1-P2V2) = mR(T1-T2)/n-1 AS we know R/n-1 = Cv and Cp/Cv=1 also considering m=1 W=Cv(T1-T2) but in textbook it is quoted as...
  19. J

    Why Does Pulley Require Less Work to Lift Mass?

    As I understand it, pulleys will reduce the force needed to lift objects but require a greater distance. As the number of pulleys increase, the force decreases. But for all cases of pulleys, the work required to lift a given object to a given height will always remain the same. When I attach...
  20. A

    Work done by friction of a box

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  21. KiNGGeexD

    How Do You Calculate Work Done by a Changing Force?

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  22. S

    Using Stokes law, calculate the work done along a curve

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  23. B

    Work done along the curve in 3 dimensional space

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  24. KiNGGeexD

    Calculating Energy Required to Rotate a Spiral Spring by 180 Degrees

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  25. T

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  26. P

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  27. A

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    Problem: Points A and B each have an electric potential of +9 V. How much work is required to take 2 mC of charge from A to B? Equation: V = W / q 9V = W / .002 C W= .018 J. This answer I'm getting is incorrect and I'm not sure what else to try. Any help in the right direction would...
  28. Sen.Lemonsnout

    Work done by a person climbing stairs

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  29. N

    How does pressure and volume affect the work done by gas in a vacuum?

    I learned that work done by gas is zero when a gas expands in vacuum. But the volume and pressure of the gas change.Then how work done by gas is zero?
  30. W

    Work done shortening string of rotating object

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  31. M

    Work done by an external force problem help

    Homework Statement a rope is used to pull a 3.57kg block at constant speed a distance 4.06m along a horizontal floor. the force on the block from the rope is 7.68 N and is directed 15 degrees above the horizontal. a) calculate the work done by the ropes force b) calculate the increase in...
  32. M

    Work done is the area under a voltage against charge graph

    Homework Statement Homework Equations Area of a triangle is 0.5 × b × h ΔW=VΔQ The Attempt at a Solution I drew a straight line graph from the origin with end point 4.5V 9.0 microF energy is a work done = .5QV There is a mark in the mark scheme for ΔW=VΔQ explained...
  33. B

    Work done in moving the plates of the capacitors

    A parallel plate capacitor of circular cross section r>>d, and separation d. It is charged to potential V then disconnected from the circuit . What will be the work done in moving the capacitor from d to d1? Answer: Here the initial energy is 1/2CV^{2} Where C=Aε/d While moving the capacitor...
  34. C

    Work done - moving a charge in an electric field

    work done -- moving a charge in an electric field Homework Statement Q=10uC from origin to (3m,pi/4,pi/2) E=10r unit r + 5/(rsin(theta) unit phi V/m answer is -475uJ I found this problem in a reference book that gave answers, this problem is similar to a homework problem...
  35. ajayguhan

    What is the reason behind the stress being zero when stretching a rod?

    I know that I'm wrong but couldn't find where I'm Stress=internal force /area When the body is in equilibrium, force applied equals internal force.therefore stress=force applied/area Let us stretch a rod by two equal and opposite force.,say f and -f...thus total force is zero Stress=...
  36. T

    Graphing the work done by a force along paths

    Homework Statement Evaluate the work done W = op∫ F\bulletdr By the two dimensional force F = (x2, 2xy) along the following paths from the origin to the point P(1,1): 1) This path goes along the x-axis to the point Q(1,0) and then directly up to the point P(1,1). 2) Along the path y...
  37. K

    Work done by rotating a ring in a magnetic field.

    Homework Statement Our teacher isn't very descriptive: A ring of radius "a" and resistance "R" is placed at the center of a long solenoid with "n" turns (assume the solenoid is longer and wider than the ring) with its axis lined up with that of the solenoid. Find the amount of work done to...
  38. M

    Work done against friction for a car with 125 KJ KE.

    "A 1200kg car as kinetic energy 125kJ at the bottom of a 20 degree slope. It rises to a height of 10m. Calculate work done against friction." Relevant equations: Work = force x distance in direction of that force Work = KE = 1/2 x m x v^2 I'm not really sure where to start...tried...
  39. C

    Power Output & Work Done by a Motor

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  40. D

    Question on Work done by horse pulling a wagon.

    Homework Statement How much work did a horse do that pulled a 200-kg wagon 50 km without acceleration along a level road if the effective coefficient of friction was 0.060? Homework Equations W=Fnet * d Force of friction= µmg The Attempt at a Solution...
  41. S

    At what angle is the work done minimised?

    The problem as it appears on the problem sheet: A block of weight mg = 500 N is sitting on a horizontal floor. The coefficient of kinetic friction is \mu_{k} = 0.4. In class, we determined at what angle from the horizontal I should pull on the block if I'm weak and need to minimise the force F...
  42. S

    Work Done per Unit Charge vs Current

    A trivial question. I know that current is the amount of charge passing per unit time across a area. And Potential difference is change in potential or change in potential energy per unit charge or work done per unit charge. And also from Ohms law, V is directly proportional to I. So...
  43. J

    Does Zero Work Imply Unchanged Speed and Velocity?

    Homework Statement An object is moving along some path. the total work done on the object during this process is zero. Homework Equations no equation The Attempt at a Solution A the speed of an object has decreased. B the speed of the object may have changed. C the object must be...
  44. C

    Calculating work done using vectors

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  45. S

    Is Infinite Work Possible in a Frictionless Vacuum?

    Work done= force.displacement In space, with no external forces, air drag, gravity etc if you apply a force to object if will move forever in the direction of force unless any resultant force act on it to change its momentum. In this case let's take force as 2N so we get w.d=2N.s s will...
  46. I

    Calculating the Work done from an Incline with Friction Problem

    Problem: A father pushes horizontally on his daughter's sled to move it up a snowy incline, as illustrated in the figure, with h = 3.6m and θ = 15°. The total mass of the sled and the girl is 35 kg and the coefficient of kinetic friction between the sled runners and the snow is 0.20. If the...
  47. PsychonautQQ

    Ferris Wheel work done by net force

    My textbook says that if you are on a ferris wheel that is rotating, the total work done by all the forces acting on your is zero. How is that possible? You are moving so isn't work being done to you?
  48. M

    Is Calculating Work Done by Gravity as Simple as It Seems?

    So I was thinking about the Universal Law of Gravitation, and the force of an object depends on the radial distance from Earth for simplicity. As an object travels to the center of the Earth the Fg increases as the radial distance decreases.F=(G*m*m*1)/(r^2). Knowing that the Force is not...
  49. E

    Is Work done when there is constant velocity?

    Homework Statement "You carry your 14.0 kg bag of textbooks horizontally 1.8 m above the ground, at constant velocity for a distance of 25 m. Ignore wind resistance. How much work do you do on the bag in the process?" Homework Equations W=Fd F=ma The Attempt at a Solution If work...
  50. Z

    Expanding gas - is any work done?

    Homework Statement I can't figure this out...if you have a gas in a rigid container, with a membrane separating the gas from a vacuum in the other half of the container, then remove the membrane and allow the gas to expand, is any work done? It's not expanding against force - does that make...
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