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. P

    Forces involved in principle of virtual work

    The answer is as such: There’s only one way for the system to move: the rectangle can deform into a parallelogramso that the left horizontal arm moves up, and the right horizontal arm moves down by thesame amount. Then the total virtual work done on the scale by the weights is zero, so thesystem...
  2. M

    Work done by power supply to maintain a constant current

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  3. I_Try_Math

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  4. A

    Irreversible isothermal Process Work External pressure not provided

    It is clear that the process is isothermal else it is not possible to find heat absorbed. $$W=-P_{ext}(\Delta V)$$ However ##P_{ext}## is not given. How do I proceed? I tried taking ##W=-(P_2V_2-P_1V_1+P_3V_3-P_2V_2)=\Delta(PV)## but it is wrong for obvious reasons.
  5. putongren

    B Exact differential and work done

    I was researching about conservative and non-conservative forces, and there is some information in a website that sates that the work done is independent of path if the infinitesimal work 𝐹⃗ ⋅𝑑𝑟⃗ is an exact differential. It further states that in 2 dimensions the condition for 𝐹⃗ ⋅𝑑𝑟⃗ = Fxdx...
  6. A

    Why is the work done double its expected value? (conveyer belt)

    The question was this: My calculations show that the answer should be equal to work done on crate to make it reach the same velocity which is equal to 216 J but the answer given is 432 J It is believed that extra energy is needed to overcome friction but friction is an internal force and...
  7. E

    Work done pushing a spring from the side

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  8. E

    Work done by a normal force (or rather, work NOT done)

    This question states that the normal force of the stairs on the woman does NO work. I do not understand how this can be. I would reason like this: The woman propels herself up the stairs using her legs. Her legs push down against the stairs, and the consequent normal force pushes upwards on her...
  9. nav888

    Work done by a force down a ramp

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  10. Mohmmad Maaitah

    Work done by gravity and the minus sign

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  11. nav888

    How does the calculation of work change for a rotating or non-rigid object?

    Here is the question, I am struggling with it as in all the past questions I have done it didnt matter if you worked out the work done by each force and then added it all together or if you added the forces together and then worked out the work done by the total force, but here the net force is...
  12. Lotto

    B What is meant by "upper limit of work done on Earth"?

    I think that the work is meant to be work done for instance in power stations. Or is it similar to work I do on a body when I lift it for example? But how can we then do that work on our Earth? I just need to understand the task, otherwise I want to solve it myself. The problem involves...
  13. S

    My Mistake? Understanding Friction Force & Work Done on Snowy & Icy Surfaces

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  14. M

    Finding heat exchanged work done to compress gas

  15. M

    Understanding Isothermal Work: Solving the Gas Compression Problem

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  16. M

    Work done on a gas when it is compressed quasi-statically

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  17. H

    Finding the work done by a block

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  18. Darmstadtium

    B Is the Definition of Work Done Applicable to Free Fall?

    For example, if a ball is from a certain height, the work done is 0 as there is no change in total energy the Ef =Ei. However, there is a constant force applied over a certain distance, suggesting work is being done. Which aspect am I forgetting/missing? Or is it that the definition of work done...
  19. M

    Finding the work done by Spiderman

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  20. S

    I Work done "against centrifugal force"

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  21. haha0p1

    How do I find the work done for a 100 N downward force?

    I have found the work done for 100 N, 70 N and 30 N force, but I don't know how to find work for 100 N force that is acting downwards. Force 70N: W=F×d = 70 ×0=0 Nm (Force is perpendicular to the distance moved) 100 N force: W=F×d=100×0.5=50 Nm 30N force: 30×-.5= -15Nm. Please check whether...
  22. C

    Help Calculate Work Done in Adiabatic Process & Fill Table

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  23. MatinSAR

    Is the Work Done by a Variable Force Non-Conservative?

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  24. M

    A Calculate work done by a time-dependent pressure to a spherical hole

    Hello, Suppose I have a spherical hole in a elastic infinite space. I apply a time-dependent pressure to the inner surface of the spherical hole. I know p = f(t). If I only consider this as an elastic problem, no failure happened, how can I calculate the work done by p during the time from 0...
  25. M

    A Calculate the work done by pressure rupturing a spherical containment

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  26. H

    I Exploring Work Done in Quasi-Static & Non Quasi-Static Expansion

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  27. S

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  28. pandatime

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  29. S

    Work done on a falling elevator by a spring + gravity

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  30. Tesla In Person

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  31. Tesla In Person

    Internal Energy of Gas and Work done

    This is a thermodynamics question. A gas absorbs 10 000 J of heat , it releases 3000 J and does 2000 J of work. How much has the internal energy varied? So I did 10 000 - 3000 -2000 = 5000 J so internal energy decreases by 5000 J. But the correct answer is A) it increased by 5000 J . How ?
  32. S

    Work done in adiabatic compression

    The equation I know for adiabatic work is W = P1V1((V1/V2)ϒ-1 - 1))/ϒ-1, but this involves ϒ, but I can use ϒ = Cp/Cv = Cv+R/Cv = 1 + Cv/R, does this seem correct? But I still have a P1
  33. LCSphysicist

    Work done by gas expanding into a cylinder+piston system

    I will summarize briefly my reasoning for both letters, since the answer is immediately after that: A) The work is quasi-static, and the pressure is approximatelly constant and equal to the atmospheric pressure, so the works is $$W = -p\int dV = -p_{0} (V_{0}-V)$$ B) The work is fast, fast...
  34. Poorneshwar 2

    I Work done by a gas in a heat engine which compresses a spring

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  35. A

    Work done by cord on the pulley

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  36. J

    Some confusion about work done to separate charges

    The reason I'm posting this is because I'm confused about the reasoning behind the equation. For oppositely charged particles, wouldn't work done increase with distance? According to this equation you get a higher magnitude of work done the smaller the distance. How can that be? I got the answer...
  37. rudransh verma

    Work done in moving a body up an incline

    ##W=mgh=100(\sin 37)2=-120J## Right answer! But the question is asking work done by the person. So again I wrote two eqns ##F_N\sin 53+F_D\sin 37-100=10.2a_y## ##F_N\cos 53-F_D\cos 37=-10.2a_x## I just need ##a_x## and ##a_y## to solve.
  38. rudransh verma

    Why can the potential energy at any point be chosen to have any value?

    The force is -Mg and distance is L/3. So W=-MgL/3. Not right! Maybe it’s done using COM but there is no additional information is given.
  39. S

    Work Done by Friction & Gravity on Incline: Explained

    So for the work done by the kinetic friction, the displacement along the incline is ##s## as given. What I canNOT understand is why the displacement in the y-direction is used for the work done by gravity i.e. ##W = -mgh## where ##h## is the displacement in het y-direction. This instead of the...
  40. S

    Work done on a pendulum by gravity

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  41. S

    What mistake am I making when calculating work done by a force?

    The answer key is zero because the areas are above and below x-axis and have equal magnitude so canceling out each other. But I am confused about the solution Area 1 is above x-axis but I think the work done is negative since the sign of ##F## and ##x## is opposite. Work done on area 2 is...
  42. D

    B Why does the work done by a weightlifter result in a net energy loss?

    Hello, I'm getting a little confused and would appreciate some clarification. If a weight lifter lifts a weight of 2500N a distance of 2m, the work done by the weight lifter's force on the weight is 5000J. The work done by the weight force due to gravity is -5000J. The weight lifter then...
  43. rudransh verma

    B Work done in lifting and lowering an object

    ##\Delta K=K_f-K_i=W_a+W_g##.(##W_a##, work done by applied force and ##W_g##, work done by gravity) In case of uniform motion with velocity u, kinetic energy is equal. Change is zero. ##W_a=-W_g## If one force transfers energy into the system then the other takes out of the system. Energy of...
  44. S

    Work done on dipole and potential energy in uniform electric field

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  45. P

    Calculating Work Done by Gas at Constant Pressure

    A gas with a volume of 8m^3 with a temperature of 400K gets warmed up to 550K with a constant pressure of 200Kpa. How much work has the gas done to the environment? I think i might need to use the ideal gas law for this which is: ( P * V / T = N * K ) Where V is volume, T is temperature and N...
  46. S

    Is the work done by friction on a moving car's wheel positive or negative?

    The answer key is (b) but in my opinion it should be (d) because I think about work done by friction on wheel of car when the car moves. Let say the car moves to the right, then the wheel will rotate clockwise and the direction of friction acting on the wheel by the road will be to the right and...
  47. P

    Recognizing Thermodynamic Scenarious (Work Done)

    Let me start out by saying it's been a LONG time since I've touched any thermodynamics but I'm starting to think that the answer for all 3 parts are the exact same (at least for work) Namely ##W = \int_{\frac{L^3}{2}}^{L^3} P(V) \, dV = NkT_0 \int_{\frac{L^3}{2}}^{L^3} \frac{1}{V} \, dV =...
  48. hayke101

    What is the Conservation of Energy in Spring Work at an Angle?

    ..
  49. Iwanttolearnphysics

    About Work done when velocity is constant

    Here's where I got the questions: These are from a worksheet I downloaded online: Answer Key The answer key says that the answer to the first question is 500J and for the next question it's 433J. It says constant speed though, so I don't understand why the answers aren't zero. I get how they...
  50. H

    What is the meaning of work done for non-uniform circular motion?

    This is my solution ,and I just use the definition .But I still feel unclear about the concept of non-conservative force.$$ W = F x = 30N (\frac{1}{2}\pi r ) = 56.2 J $$ $$ E_{system} = \Delta K + \Delta U = W $$ $$ (K_{f}- K(i))+(U(f)-U(i)) = W $$ $$ (\frac{1}{2} *m{V_{f}}^2...
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