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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Force Applied but No Distance Travelled

Suppose I push on a wall with a constant force of 5 N for 10 s. The wall won't move and hence no work will be done on the wall. However, pushing requires energy. How can I find out how much energy I ...
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How to find the work of each force acting on a block?

A push of 200 N moves a 100 N block up at 30º inclined plane. The coefficient of kinetic friction is 0.25 and the length of the plane is 12 meters. a. Find the work done by each force that acts on ...
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Virtual Work and Arbitrary unit vectors

I was recently watching a lecture on MIT OCW where they were talking about Newton's Laws for a pulley system. The professor solved a problem pretty quickly using a method called virtual work. I tried ...
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Work done by spring force

Consider a spring connected to blocks on it's ends lying on smooth horizontal table. Now let the right end block be displaced $x_1$ and left end be displaced $x_2$ from the mean position such ...
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On source of heat energy dissipation in a system

Suppose we have a block of mass m which was at rest on a rough floor and is now given an impulse towards a wall.It is given that the collision with wall is perfectly elastic and no energy is lost in ...
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The potential at a point

According to my book, 'The potential at a point is said to be 1 volt when 1 joule of work is done in bringing 1 coulomb charge from infinity to that point.' But I wonder how it is possible. As the ...
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How can i calculate the friction force in this problem? [on hold]

Question: if the engine of a 1400kg car uses 25kw to maintain an average speed of 17m/s, calculate how much friction is acting on the car. my try: p = $\frac{w}{t}$, w = ΔKE, KE = $\frac{1}{2}mv^2$...
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Work done by a varying angle

I know that work done by a constant force is $W=\vec{F}\cdot \vec{x}$, and that work done by a variable force is $\int \vec{F} d\vec{x}$. However, how do you calculate work done by a varying angle?
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When is work actually done?

Wikipedia says: For example, when a ball is held above the ground and then dropped, the work done on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to ...
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On work done by internal forces which is coming out to be not equal to zero

1) Let us consider a block which explodes due to some internal mechanism into two smaller fragments of equal masses.The system was initially at rest and now is having some finite kinetic energy(due to ...
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Energy dissipation and work of adherence force

Assume you are pushing a heavy item. But it's not moving. So there is no work, and there should also be no dissipation of energy $P=F v=0$, since the forces don't work. But we see that it does demand ...
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Difference between the work done by three masses on different situations

We have 3 particles, with mass $m_{i}$ What's the difference between: i) Putting each one in a positión $x_{i}$ one by one, and ii) Putting the three at the same time in positions $x_{i}$, in both ...
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Does a static-firing rocket engine do work?

Is the "working fluid" doing any work during a static-fire of a rocket engine. Since the rocket is held stationary, there is no work being done on the rocket right? However, is the exhaust doing work ...
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Does the magnetic part of the Lorentz force do work?

The magnetic part of the Lorentz force is $$\vec F_L=q\left(\vec v\times\vec B\right)$$ As this force is always perpendicular to the direction of the movement, we learned that no work is done by it. ...
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Why electric potential energy at a point is the same as amount of work done to bring the charge to that point from infinity?

Let's consider a positive charge at a point in the space. Now, if we want to bring a another positive charge to a point within the electric field of the first charge, then we have to do some work ...
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Does a normal reaction do work too? [duplicate]

On backflipping off a wall, the wall applies an equal and opposite force that pushes the person in the opposite direction of the applied force. Or, on simply pushing a wall, the wall pushes back. Does ...
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Work done by friction in a Half-Gaussian path [duplicate]

EDIT This is not duplicate of Work done by friction in a complicated path, because here exact path type is given (Gaussian), so that full integration over path can be performed and results achieved ...
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Why is work equal to force times displacement?

This is how I think of what work is.I am sure I am wrong somewhere because I shouldn't be coming to the conclusion that I am coming to.It would be helpful if you would point out where this conceptual ...
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Work of a fixed wall

In this link here, What work is done by the wall when a ball hits it? The answer to the question if a wall performs work when hit by a ball was, that the wall does no work if it isn't displaced. But ...
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Work done on object in space

Suppose we apply a force of 1N on an object in space,due to Newton's 1st law of motion it should go on forever,therefore it's displacement goes on increasing.Does that mean that work done is infinite,...
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Work done by friction in a complicated path [closed]

A block of mass $M$ is taken from point $A$ to point $B$ in a complex path by a force $F$ which is always tangential to the path. We also have coefficient of friction as $K$. What will be the work ...
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How Much Power Is Required to Hover?

Suppose I have a spaceship that weighs 1,000 kilograms. I take it to the surface of the planet with a gravitational acceleration of 10 meters per second-squared. The planet has no atmosphere and I'm ...
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Is the Olympic running race fair? [closed]

I noticed that the 200-meter sprints are conducted on curved tracks. (See this video: world championship semifinals 2009) Isn't that weird? I mean, just look at the curvatures of each lane! (Source)...
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Friction on the surface of a pulley

1)Is friction between the part of string in contact with the pulley and the pulley same throughout the entire surface of contact ? 2)what is the linear work done by this friction when the pulley ...
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How is energy conserved in terms of “Work”

Basic equation of work is given by $F\cdot s$. When work is done, the energy is stored either in form of potential or kinetic. My question arises when we look at a case of applying $m g$ of force ...
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Rotational Work done by Friction

(Okay so I have asked this in a previous post but I think this should be a separate question) Consider a cylinder performing accelerated pure rolling (Static friction is non-zero) on a sufficiently ...
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Why when change in kinetic energy equals to zero the work done by two opposite forces is equal even if displacement takes place?

For example if we pull a block on an incline. Then the force of gravity i.e. $mg \sin(θ)$ will be equal to force applied so that the net work done will be zero. But if $mg \sin(θ)$ is equal to force ...
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Arriving at the definition and purpose of enthalpy

I've been trying to understand the conceptual idea and purpose of enthalpy for the past two days. From what I've learned, enthalpy is defined as: $$E = U + PV$$ This leads me to my first question. ...
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Proof for condition of a Force being conservative

While studying Mechanics, I came to know about a way to test whether a force is conservative. Check whether the expression for the Work done is solvable without the path of the object that is $\int \...
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3answers
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Why does PV work consider total pressure instead of net pressure?

In physics, we define work as: $$W = F_{net}×d$$ However, in physical chemistry, PV work is calculated as: $$W = P×ΔV$$ Why is total pressure used instead of net pressure? For example, if a gas is ...
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Why does entropy allow heat to be converted to work?

Physical chemistry has made me question everything. Recently, I was thinking: "why is it even possible to convert heat to work?" From what I learned, a heat engine can take energy in and convert it ...
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What is providing the force required to move the conductor in a changing magnetic field?

Earlier, I came across this problem. It goes as, "The current in the long wire is suddenly switched off. Neglecting gravity, what is the velocity acquired by the loop" Attached figure: Now, my ...
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Discussion regarding work done? [closed]

Suppose I take a box with some masses and pull it along the table at a constant speed. In this case, there is a force pulling to the right (the string) and a frictional force pulling to the left. ...
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If a thermodynamic cycle on a Pressure-Volume diagram has internal irreversibilities, what does the area enclosed by the cycle represent?

When a cycle is internally reversible, the area enclosed by its P-v or T-s diagram is the net work, but what about when the cycle is internally irreversible? Is it net useful work on the surroundings ...
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How can a spring contract when magnetic field cannot do work?

When a spring is kept in a magnetic field and current is passed through it, its edges act as parallel conductors and due to the action of Lorentz force, they pull themselves together. A spring ...
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For the potential difference, how is it that $V=W/Q$=$U/Q$ when $U$ and $W$ are negatives of each other?

I'm currently studying electric potential and am somewhat overwhelmed by all of the different equations and their iterations. For instance, the first definition I learned was that: $$\Delta{V}=V_b-V_a=...
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Not able to understand a concept from Classical Mechanics by H. Goldstein [closed]

I was reading classical mechanics by H. Goldstein and I came across the calculation of total potential energy of a system of particles. I am not able to understand what this derivation is conveying ...
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Doesn't the work $W = \int F \, dx$ count only the work done by the outermost point of a spring?

When we use the integral to calculate the work done by the spring force, then according to my interpretation, we are only calculating the work done by the outermost point on the spring. Why don't we ...
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Work on an object in equilibrium

I heard somewhere that when an object is in equilibrium on the flat bottom of a hill that it will require work proportional to $dx^2$ when moved the small distance of $dx$. I thought that it would be ...
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Confusing work done on a particle

I'm going to ask a simple question, but it's bothering me. We all know that work done by a force which is perpendicular to its path of motion is zero. Suppose I keep a chunk of mass in a perfectly ...
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simple work and kinetic energy problem (baseball)

problem says: A baseball player throws a ball with a mass of $0.150kg$ with a speed of $40.0 m/s$ and an angle of $30$ degrees. What is the kinetic energy of the ball when it reaches the highest ...
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What is the meaning of maximum work in this thermodynamics question?

I am having difficulty understanding this problem. Given question :- A mass of 0.25 kg of air in a closed system expands from 2 bar, 60°C to 1 bar, 40°C while receiving 1.005 kJ of heat from a ...
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Two Opposite Point Charges: Infinite Potential Energy?

If I had a fixed point-charge ($q_1$, +) and I placed another free-moving charge ($q_2$, -) some distance away, what is the potential energy between them? The opposite charges attract drawing $q_2$ ...
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If magnetic force can't do any work, then how can we define a potential?

I am confused about the idea that magnetic forces do no work. If something has a potential, then it has energy and hence can do work. I am using the logic of electric fields for this reasoning. I have ...
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What is the physics interpretation of work done of zero when moving a charged particle on an equipotential surface?

Assume I have a test charge of + 1 coulomb. If I move the test charge from a point with potential of +9 volt to another point with potential of -1 volt then the work done by me is -10 joule. This ...
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Can a conservative force do not conserve mechanical energy?

Let us define a conservative force as being a force whose work is path independent. Then, in particular, a vanishing force is conservative. If a force acting on a particle can be written from a ...
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Work - Energy confusion when movement is vertical/up a slope

I've always thought of work done on an object as the energy transferred to it. This explanation, however broke down when I came across the following situation : A block of mass $m$ is transported to ...
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Gravitational Potential Derivation

The definition of Gravitational Potential at a point is the work done per unit mass in moving it from infinity to that point. However the work is positive and if you perform the integral you get a ...
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Comparison of work in reversible and irreversible processes

My teacher said that there is always wastage of work in irreversible process and that work in an irreversible process is always less than that in a reversible process even if one is adiabatic and the ...
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Why is it assumed that magnetic forces arising from magnetic fields do not do work on a current carrying conductor?

Imagine a long, thin current carrying conductor carrying a current $I$ and moving through space with a velocity $\mathbf v$. If there exists a magnetic field such that there is a force on the current ...