Work done Definition and 1000 Threads

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. K

    Work done by a force over a distance, relative or absolute?

    When we calculate the work done by a force applied on an object (suppose force and movement are in the same direction and a constant force) do we take into account the relative distance ot the absolute distance. When saying relative distance i mean if the object is moving on top of a platform...
  2. D

    What is the Work Done During a 100m Sprint?

    Homework Statement How much work per step per leg in the race? How much work must he (single leg) squat to equate 1 step of work in the race? The given variables are: Displacement: 100 meters Time: 9.65 seconds runners weight in kg= ? 100 steps to complete 100m race, alternating legs...
  3. J

    Finding Work done under a graph?

    Homework Statement [/B] A force acts on an object along an x axis. The force varies with position as shown in the graph below. On the graph, F = 52.0 N. Find the work done by the force as it moves the object from x = 0 to x = 15.0 m. Homework Equations [/B]The Attempt at a Solution So what...
  4. J

    Work done on a shopping cart by friction when being pushed

    Homework Statement A grocery cart with mass of 19.3 kg is pushed at constant speed along an aisle by a shopper who exerts a force of 13.1 N on the cart at an angle of 18.3 from the horizontal. The aisle is 15.1 m long. The coefficient of friction is 0.0658. Find the work done on the cart by...
  5. Mr Davis 97

    Work Done by Person Carrying Groceries Up a Staircase

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  6. A

    How is the minimum work needed to push a car up an inclined plane calculated?

    Homework Statement What is the minimum work needed to push a 1000-kg car 300 m up a 17.5 degree incline? A. Ignore friction B. Assume the coefficient of friction is 0.25 Homework Equations W = F*d Net force = ma The Attempt at a Solution At first I did: Work = F*300*cos17.6 but I later...
  7. A

    How Does Gravity Affect Kinetic Energy in a Glider System?

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  8. M

    How to Calculate Work from F vs x Graph?

    Homework Statement x1= -2, x2= 2 F1= 1, F2= -2 Graph in uploaded image Homework Equations w= F* del x* cos(theta) The Attempt at a Solution I am trying to find the area under the points of F and x but it has an irregular shape and i don't know what to do? Should i do w= (f1-f2)(del x)?[/B]
  9. Z

    Work done by a tangential force

    Homework Statement The 4-kg ball and the attached light rod rotate in the vertical plane about the fixed axis at O. If the assembly is released from rest at and moves under the action of the 60-N force, which is maintained normal to the rod, determine the velocity v of the ball as approaches ...
  10. esha

    To calculate work done from a graph

    In the given question part (a) I don't understand why the work done is negative? The answer says that the displacement is along positive x direction (i understand that) while force acting on the particle is along negative x direction ( why is that? since it appears that as the value of x is...
  11. S

    Calculating Work on a Falling Raindrop

    1. The problem statement, all variables, and given/known data How much work does gravity do on a 1.9-mg raindrop as the drop falls to the ground from a cloud 2500 m above the ground? Homework Equations W = FΔx F = ma The Attempt at a Solution I thought this problem would be pretty...
  12. A

    What should be the work done here?

    Homework Statement If you apply a force F with the x component =-6.97 N and the y component = 8.47 N on a car which moves along the x-axis by a displacement of 3.37m. What is the work done on the car by your force in J? Homework Equations W=Fxd The Attempt at a Solution I think that the...
  13. H

    Work done running on an inclined treadmill

    Why does it cost roughly the same effort to run against an inclined treadmill as up a hill of the same inclination? That is neglecting the movement of the legs and the bobbing up and down as we run and the wind resistance. I remember being told in school physics that there is no work done unless...
  14. B

    Determine work done by electric field

    Homework Statement Given electric field ##\vec E = 6x^2\hat i +6y\hat j+4\hat z## v/m Find ## V_{MN}## if both M and N separate by M(2,6,-1) and N(-3,-3,2) Homework Equations The Attempt at a Solution here i find ##V_{MN}## by unit vector from N to M is ##\frac 1 {\sqrt (115)}(5\hat i +9\hat...
  15. O

    What is the total amount of work done by friction?

    Homework Statement Consider a rope of mass M and length L, resting on a horizontal table, as shown in the figure. The coefficient of kinetic friction between the table and the rope is μk. Let's consider the work that's done by friction as we slide the rope off the table. a.) Consider a small...
  16. E

    Work done by gravity and by a spring

    Homework Statement I have two objects that slide without friction on a circle of radius R, oriented in a vertical plane, as seen on the attached photo. The heavier object (mass = 3m) is attached to a spring with an unstretched length of zero and spring constant k. The fixed end of the spring...
  17. NoahCygnus

    Work done on the centre of mass and kinetic energy of system

    If we have two objects forming an isolated system and their centre of mass is ##X_{com}##, we know by work energy theorem that work done on centre of mass will be ##\int F_{ext}.X_{com}= 0## as no external force is acting on the system. However, if there is internal forces between the objects...
  18. NoahCygnus

    Net work done on Earth-object system and potential energy

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  19. F

    Work done pumping air into a bottle

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  20. S

    Are Both Formulas for Work Done in an Electric Field Correct?

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  21. RJLiberator

    Isothermal Work Calculation for an Imperfect Gas

    Homework Statement An imperfect gas obeys the equation (p+\frac{a}{V^2_m})(V_m-b)=RT where a = 8*10^(-4)Nm^4mol^(-2) and b=3*10^(-5)m^3mol^(-1). Calculate the work required to compress 0.3 mol of this gas isothermally from a volume of 5*10^(-3)m^3 to 2*10^(-5)m^3 at 300K. Homework Equations...
  22. Nikhil Rajagopalan

    Is the Work Done by Static Friction Always Zero in a Round Trip?

    Friction is said to be a non conservative force. And I see various sources state that work done by a non conservative force on a round trip is always non zero. But is that always true? In a case where a coin is placed on a turn table, and the table is rotated, and the coin does not move during...
  23. R

    How do I find the work done in an adiabatic process?

    How come ##adiabatic \,work = C_v(T_2 -T_1)##
  24. tze liu

    Where is the work done coming from in Helmholtz free energy

    Sorry,i want to ask a question here the note said the volume is "fixed" here. if the volume if fixed,how comes the work done(because no change of volume) here i totally get lost here thank
  25. F

    Using parameterisation to calculate work done by force

    A force F = -K(yi + xj) (K is a positive constant) acts on a particle moving in the x-y plane. Starting from the origin, the particle is taken along the positive x-axis to the point (a, 0) and then parallel to the y-axis to the point (a, a). What is the total work done by the force F on the...
  26. Timothy Schablin

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  27. psy

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  28. T

    TagEqual force for different times: Pushing a car slowly vs quickly

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  29. Mr Real

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  30. B

    Maximum work done in a Carnot Cycle

    Given that in a Carnot Cycle the two adiabatic processes are essentially equal and opposite in magnitude the total work done by the cycle is in the two isotherms. The total work of the system is generally given as -NR(Th-Tc)ln(Vb/Va). Does this mean that the work done by a monatomic ideal gas is...
  31. EM da Costa

    Calculate work done on charged object between plates

    Homework Statement I am trying to calculate the theoretical time that it takes for a small piece of aluminium foil on a bottom plate to reach a top plate. The plates have a potential difference created by a 3kV Cockcroft–Walton generator. The plates are short cylinders with a surface area of...
  32. A

    Work done on real thermodynamic data

    Homework Statement I have the data for a p-v diagram from experiment of a fluid (the fluid is unknown). The data is attached below as the crosses. It also has the approximated ideal cycle for that data. Does anyone know how to find the work done for this real experimental data? Maybe a MATLAB...
  33. yecko

    Solving Chain Work Problem: Find mgh | Physics Homework Help

    Homework Statement http://i.imgur.com/TdPWVgr.pngHomework Equations WD=mgh The Attempt at a Solution mass per length=0.8kg/m mgh= ∫(0,10)(0.8g(10-y))dy=[8gy-0.4y^2g](0,10)=80g-40g=40g However, the answer is 20g whats wrong with my calculation? thanks
  34. knc

    What is the Work Done by a Gas in a Cycle?

    Homework Statement Homework Equations PV = nRT \\ W = - \int_{V_i}^{V_f} P dV \Delta E_{int} = Q + W The Attempt at a Solution a)[/B] Since this is a cyclic process, the change in internal energy of the system is 0. \Delta E_{int} = 0 The process causes some ice to melt, meaning heat...
  35. hackhard

    Is Work Done by a Voltage Source Positive or Negative When Current Opposes EMF?

    Is the work done by a constant voltage source positive or negative when current is opposite to emf?
  36. T

    How Much Work Does Kinetic Friction Do on a Sliding Block?

    Homework Statement A 5.72 kg block is released from rest on an inclined surface. The incline makes an angle of 25.0 degrees relative to horizontal. The block is known to be traveling at a speed of 1.33 m/s after sliding a distance of 2.60 m along the incline. How much work was done on the block...
  37. M

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  38. Z

    Work Done by Gravity and Derivation of G.P.E.

    I came across this website and I intend to find out more about work done by gravity and derivation of gravitational potential energy (Sorry, the thread name is too long, so I abbreviate it as G.P.E.) Ok, here is the problem. I am quite confused with the calculation of work done against gravity...
  39. R

    Change in internal energy when water is heated from 0 to 4c

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  40. R

    How Is Work Calculated with a Nonconstant Force?

    Homework Statement An object is subject to a nonconstant force f = (6x^3 -2x) ihat such that the force is in Newtons when x is in meters. Determine the work done on the object as a result of this force as the object moves from x = 0 to x = 100 m Homework Equations w = f * d The Attempt at...
  41. F

    Work done on an object in a spring pendulum

    Homework Statement The drawing shows three situations in which a block is attached to a spring. The position labeled "0 m" represents the unstrained position of the spring. The block is moved from an initial position x0 to a final position xf, the magnitude of the displacement being denoted by...
  42. R

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    Homework Statement : [/B]A thermally insulated closed copper vessel contains water at 15°C win the vessel is shaking vigourously for 15 minutes the temperature rises to 17°C the mass of the vessel is hundred gram and that the water is 200 g capacities of copper and water for 20 J/kg K and 4200...
  43. V

    What is the work done in this case?

    Homework Statement A spring (k = 500 N/m) supports a 400 g mass in a vertical position. The spring is now stretched 15 cm and maintained at the stretched position. How much work is done in stretching the spring by 15 cm? Is this work dependent on the magnitude of force applied while stretching...
  44. G

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    Hello. First, look at the figure describing Carnot's cycle. In 1st step (A → B) and 2nd step (B → C), I fully understand that the work done on the pistol (surrounding) by the gas (system) is dW = pdV where dV = Adl since F = pA is the only force on the pistol from the gas (I assumed there...
  45. Nikhil Rajagopalan

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    Dear Experts, Trying to analyze the work done by internal forces in a very simple two particle system which is attracted to each other with a constant force, i performed calculations based on two frame of references, 1.The center or mass frame of reference and 2. Frame of reference of one of the...
  46. Ameya Darshan

    Man Jumps Horizontally: Work Done by Man

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  47. Nikhil Rajagopalan

    Work done due to static friction in a boat-man system

    In a classic problem where a man walks along the length of a boat floating on the surface of water without friction, Should the net work done due to static friction between the man and the boat be zero. If the length of the boat is L, its mass being M, and the mass of the man being m, the...
  48. jlmccart03

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    Homework Statement The membrane around a cell normally has layers of charge that create a potential difference between its outer and inner surfaces. This difference is about 72 mV . When a singly ionized potassium ion moves through a channel in the membrane passing from the outside to the...
  49. T

    Work done by a Carnot Engine. Melting ice

    Homework Statement The problem is that a Carnot contains Boiling water in the hot reservoir and ice water in the cold reservoir. Given that 0.0400kg of ice is melted in 5 minutes, what is the amount of work done by the engine. Homework Equations Qh/Qc=Th/Tc W=Qh-Qc W=(1-Tc/Th)Qs q=mHf...
  50. Passionate Eng

    How does a magnetic force affect the movement of charges and magnets?

    If magnetic force does not exert work on moving charges, how could a current loop immersed in a magnetic field rotate and how could a magnet attract or repel another one?
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