# Questions tagged [work]

The product of the force on an object and the displacement the object undergoes along the direction of the force.

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### Confusion in definition of Potential Energy

Potential energy is defined like this. $ΔP.E=-W_{AB}$. This means that the potential energy at point A minus potential energy at point B should equal the negative of the work done by a conservative ...
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### How can power be defined as the derivative of work with respect to time if work is not a function?

In thermodynamics, it is frequently said that work and heat are path functions with inexact differentials $\delta Q$, $\delta W$, so one can not talk about a change in work or a change in heat since ...
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### Interpretation of non-spontaneous Gibbs free energy

Good day guys, I was reading some books on physical thermodynamics, they explain that for system undergoing a chemical reaction whose $\Delta G < 0$ indicating that the reaction can then provide us ...
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### A force acts in a 30g particle in a way so that displacement acts as function of time $s = t³-4t²+3t$ in SI units. The work done in first 4 sec is: [closed]

The formula for work is $\vec F\cdot\vec s=Fs\cos\theta$ or you can use integral operators for the same But by doing so, I am getting two different answers. One is 5.4J and one is 5.28J. The question ...
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### Two rings, a frictionless rod, a string and a hanging mass [closed]

It's been days I'm not been able to figure out why I'm getting an incorrect result for this problem: Two rings of equal mass $m$ can slide along a horizontal rod. The rings are linked by an ...
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### How to mathmematically direction of friction of spool?

If I have a spool of thread with a force pulling to the right on a rolling cylinder, how can I mathematically determine the direction of the friction? ...
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### Why isn't work $Fd \sec \theta$? [closed]

In the following image if force the triangle PAN was right angle at P then the component of force in the direction of displacement would be $F\sec\theta$ so work $F*Displacement(AC)*\sec \theta$. I ...
1 vote
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### How can the energy of a system increase even if net work done on it is zero?

Imagine two blocks of mass 1kg placed on a horizontal frictionless surface. Now, if I apply 10 N on the right block in the right direction, and on the left block in the left direction, both the ...
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### Why is Power in an electric circuit equal to $VI$? [closed]

Where did this formula come from? Everyone I asked just told me to substitute values of in ohms law to derive this but no one told why is power equal to voltage * current. Part of the reason for this ...
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### Would one be pushing as much as their weight with this machine?

I was looking at the following machine in the video below, and was wondering, would one be pushing as much as their weight? https://youtu.be/a_CGlAnxO5c It looks sort of like a chest press machine but ...
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### Why does the work done depend on the frame of reference? [duplicate]

If I pushes a box due east for 1m by a 10 newtons of force, the work I do is 1J. But, if I consider the Earth's own rotation, the box actually has moved about 1km, and the work becomes more than 1000J....
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### Energy Dissipated by Damper Infinitesimal Derivation

If we consider a damper (dashpot) element that exerts a force opposite the direction of motion proportional to the velocity, i.e. $$\vec{F} = -c \vec{v}$$ Therefore, we can consider an infinitesimal ...
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### Can any irreversible work source be simulated by a reversible work source?

In a textbook for thermodynamics, it considers a situation where work is done to a system by an irreversible work source through a thermally insulating piston, and it states "any irreversible ...
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### Newton's third law in thermodynamics

In my physics textbook, the foundation for work is derived using newton's third law, where F_surr = - F_gas, where surrounding represents a piston-cylinder device and gas is pushing against the inner ...
1 vote
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### Is Joule equivalent to Joule/radian? [duplicate]

The work a constant torque does when it moves a particle through an angel $\theta$ is given by $\tau \theta$. The work is measured in Joule, so the torque should be measured Joule/radian, but the ...
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### Sign convention of work

I am studying about reversible steady-flow work, and the author of the book states that Taking the positive direction of work to be from the system (work output) the energy balance of a steady-flow ...
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### Why does force perpendicular to the velocity change only its direction; not the speed?

While analyzing the case of a force and consequently an acceleration acting perpendicular to the velocity of a given body, I do understand that force's component along the velocity will be 0 causing ...
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### A man moves on a straight horizontal road with a block of mass 2 kg in his hand. He covers a distance 40m with an acceleration of 0.5m/s^2 [closed]

We have to find the work done by the man on the block. Can we consider the situation above as a non-inertial frame? The man is accelerating forward, therefore, a pseudo force will act on the box in ...
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### Conservative force and change in the mechanical energy

Why is work done by a conservative force equal to change in the potential energy only? Why doesn't it account for all mechanical energy, what about kinetic energy?
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### Question with work and Spring

Hey so im currently going through questions and I've become confused on this question. I was able to get an answer a different way, finding the x value by equating F = kx and solving for x, and then ...
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### What distance to use when calculating work?

What distance do you use in the W=Fs formula? Is it the distance the applier of force moved or the object who feels the force? If it's case 1) That would mean a stationary proton moving another ...
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### Work of friction along a circular path using dot product

Good day guys, I was working on circular motion and was wondering about the following: I have seen that the work done by friction along a circular path is given by $$W = F_fS$$ I was wondering if it ...
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### I'd like to know how to calculate energy required to overcome static (or rest) friction

I'm trying to solve a task using energy conservation laws. An object with a known coefficient of kinetic friction is propelled by the magnetic field horizontally. We can calculate the loss of energy ...
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### A Conceptual Doubt in a Question on Work-Kinetic-Energy Theorem

I have a doubt in this question, Diagram given below In the Question it is asked that "calculate the final velocity of the block in the figure" and in the solutions it is given that the ...
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### Conservative forces and Variation

I am currently studying "Classical mechanics by Goldstein" and have just started. The book introduced something simple. For a conservative force, the work done in taking a mass from one ...
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### Escape velocity work done problem [closed]

We derive the formula of escape velocity by using conservation of mechanical energy, where we consider that work done by external force is neglected. But to provide the velocity to send an object to ...
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### Definition of entropy as unavailable work

I've read in some sources that Entropy is a measure of how much energy is not available to do work but I'm not quite sure what this is getting at. The only thing that I could think of is perhaps ...
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### How do you integrate a physics integral? [closed]

I've only taken Physics I (w/ calc) in uni, so physics is pretty new to me, and I'm only through Calculus 2. However, I keep seeing integrals like these everywhere in physics, and want to know how to ...
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### Work and energy related [closed]

No friction In case of no friction work done will be equal to total $F$ applied? When we multiply $F$ and $s$, we are basically calculating Total Force applied, right? So does that mean total $F$ ...
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### Misunderstanding Work-energy theorem and center of mass properties

A rod is hinged at one of its ends, and released from rest when it is held parallel to the ground. The question is to find the angular velocity after the rod makes 60 degrees with the horizontal. To ...
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### Maxwell- Faraday's Equation, MotionalEmf, Work Done by Lorentz Force

A moving rod placed in a stationary U-shaped frame. When a conductor (the moving rod in this case) moves perpendicular to a magnetic field, an electromotive force (EMF) is induced according to Faraday'...
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The Problem This is the problem that originally sparked my interest: A spring of spring constant $k = 8.75 \frac{\text{N}}{\text{m}}$ is hung vertically from a rigid support. A mass of $0.500 \text{kg}... -1 votes 1 answer 66 views ### Distance-velocity relation for a body accelerated with constant power A body of mass$m$starting from rest from the origin ($x(0)=0$and$v(0)=0$at$t=0$) moves along the x-axis under the influence of a force$F$that exerts a constant power$P$. Question: How to find ... 1 vote 1 answer 60 views ### How do I write angular displacment in quaternion form? [closed] Work done is given by$W = F_ids_i$and in angular displacement moment form it is$W = \tau_i d\theta_i$. I want to get the work done in using quaternion instead. Like$W = \tau_i q_i$I cannot figure ... 0 votes 1 answer 36 views ### Work done by friction in pure rolling I just want a clarity about work done by friction in pure rolling when external force is acting. So suppose we have a ring and an external force is applied at the centre, the ground has friction. ... 3 votes 1 answer 56 views ### Why do we count external pressure to calculate work done by gas instead of using internal pressure? Does internal pressure remain constant while doing work on surrounding or we ignore it? And when work is done on system we still count external pressure 1 vote 0 answers 104 views ### Adiabatic expansion paradox [duplicate] If we let a gas expand against vacuum with a piston which is not weightless then can we call it free expansion? If yes then there is a paradox . Work done by a gas is said to be = -p( external) ... 0 votes 1 answer 44 views ### Work And Energy: Conceptual Potential Energy Doubt Our teacher told us that objects store potential energy in them according the position of the object above the ground because of gravitational force. Like we are holding a box up and it stores ... 0 votes 1 answer 61 views ### Efficiency of a cyclic processes [closed] Is there a specific formula for solving the efficiency of a cyclic process in pV diagram? I have this diagram of a diatomic ideal gas cyclic process, where${p} = 4{p_0}$and${V} = 4{V_0}$The work ... 2 votes 2 answers 74 views ### Conceptual misunderstanding of work and conservative forces and their relations I tried to calculate the work done by friction along an arbitrary surface. and this is the result I got. This system is under the only force of gravity and friction. we can see that work done by ... 0 votes 1 answer 112 views ### Work done by a gas on a piston Work done by system on the piston should be$F_{\text{sys}}\cdot(ds)$and work done by the surrounding on the piston should be$F_{\text{sur}}\cdot(-ds)\$, thus the net work is stored in the piston as ...
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The potential energy is a property of a system, being defined only for internal conservative forces. From the work energy theorem, we have $$W_{ext} + W_{\text{internal cons. forces}} = \Delta K$$ We ...