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

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Work = Force x Distance vs Displacement

The difference in using Distance vs Displacement is demonstrated in this example: Work = Force x Distance If I carry an object to and fro 10 metres, the work done would be Force x 20 metres. ...
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Where does the energy go in a rocket when no work is done?

While playing Kerbal Space Program, I wondered where my chemical energy would go when fired at 90° to the motion. It would do no work on the rocket, but all that energy has to go somewhere, right? ...
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A confusion regarding an example in The Feynman Lectures

In The Feynman Lectures, In the chapter entitled Work and potential energy, Feynman states: The work done in going around any path in a gravitational field is zero. This is a very remarkable ...
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Conservative Force and $1/r^2$

Does the inverse square law have anything to do with conservative behavior of the central forces?
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Sign of Work and potential energy in electrostatics

Conceptual question: Suppose we have a configuration of point charges. If the potential of the energy of the system is negative, this means work is positive. I'm kind of rusty with my mechanics, ...
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510 views

What does it mean to say work is path-independent when pushing an object in different directions?

If I apply a straight upward(perpendicular to ground) force against gravity of $5\ \mathrm{N}$ and lift an object "A" 10 meters, then the work done is: $$ W = F \times S = 5\ \mathrm{N} \times 10\ ...
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Why can't the work done by a non-conservative force be zero?

Why can't the work done by a non-conservative force be zero? The displacement along a closed path is always zero. So, whatever be the type of force, variable or constant, the work has to be zero. Why ...
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331 views

When can one write $a=v \cdot dv/dx$?

Referring to unidimensional motion, it is obvious that it doesn't always make sense to write the speed as a function of position. Seems to me that this is a necessary condition to derive formulas ...
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Source of energy for magnetic work?

I set two magnets on my desk such that they are experiencing attraction to each other, but due to friction with the desk, are just outside of the distance where they would snap to each other. Then I ...
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Can internal forces do work?

My Mechanics textbook claims that the sum of the work by internal forces is not generally zero. translated to English the paragraph reads: Notice about the work by internal forces: the work by ...
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What's wrong with my derivation for the spring constant? [duplicate]

An $8.00\ \mathrm{kg}$ stone at rest on a spring. The spring is compressed $10.0\ \mathrm{cm}$ by the stone. What is the spring constant? I used conservation of energy to solve this problem. The ...
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Is any work done when I walk?

I am trying to figure out the amount of work done when I walk X miles or for X minutes. So I got Work=Force x Distance and Force=Mass x Acceleration and Acceleration=(change in velocity)/time. I am ...
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260 views

Work done on stationary rocket

Suppose I have a rocket thats exerts a force (with negligible loses in mass), which cancels out the downward force of gravity. Clearly my rocket could be moving at a constant velocity (ignore air ...
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Why does it require such little energy to create the fastest thing in the universe?

I have noticed when I turn on the light switch in my house light comes from the bulb. How is this light created?(process occurring in the bulb) and why is this small amount of electricity enough to ...
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282 views

Work performed by a stationary object in a gravitational field “on Earth”

I was thinking about this problem: How much work is required to hold an object stationary in a gravitational field? or: How much energy is required to keep an object stationary in a ...
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Work done by the Magnetic Force

The magnetic part of the Lorentz force acts perpendicular to the charge's velocity, and consequently does zero work on it. Can we extrapolate this statement to say that such a nature of the force ...
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Relativity of Work

Let's say there is a man pushing a wall with a force of $-1 \text N$, and moving it $0 \text m$. Since $W = F \cdot d$, he has done $0\text J$ of work on the wall. Another man is pushing a duck with ...
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205 views

What exactly is ''electric energy''?

If the two fundamental types of energy are kinetic and potential energy, is electric energy simply the kinetic energy of charge carriers? Also, is the statement "A cell converts chemical potential ...
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I have a slight problem understanding the concept of “work”?

What I understand is that work is not the same as a car using gas or a crane lifting a car high up into the air. Let's use the crane as an example. And let me write out a few lines from the book. ...
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Does a magnetic field do work on a moving rod?

In a case such as this one, my textbook says that I might be tempted to think the magnetic force is doing work (against the moving rod). It then says this isnt the case because "charges move ...
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Paradox- Object thrown parallel to the ground will never fall down

Suppose an object is thrown parallel to the ground. The gravity acts downward (ie. perpendicular to the direction of motion of the object). The work done by gravity on that object will be given by : ...
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Why can't a magnet change a charged particle's speed?

I know that magnetic force acts perpendicular to the direction of the original velocity, so the velocity in that original direction is unchanged, but once the magnet starts acting, the particle's ...
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Is the work done walking up an escalator in the same speed and opposite direction of the escalator zero?

Work equals force times distance, but what about walking up an escalator in the same speed and opposite direction of the escalator? In the frame of the ground, the distance is zero so the work must ...
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Potential Energy Concept

Imagine a book that we lift it with a force that is exactly equal to the force of gravity so the forces cancel out and the book moves with a constant velocity. Consider the situation after the book ...
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A force is exerted on a body, kinetic energy increases but no work is done by the force. Why?

After reading the article, I was totally perplexed . I was reading the External forces and internal energy transfers in Principles of Physics by Resnick,Halliday,Walker. It goes like that An ...
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How can a magnetic field accelerate particles if it cannot do work?

A varying magnetic field can accelerate charge particles, but it is said that a magnetic field can't do any work so it should not be able to speed up charged particles, right? How is this apparent ...
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Climbing Stairs and Calories Burnt

I climb stairs to work (20 floors) every day . The least amount of work my body is doing by gaining potential energy (P.E) = mgh where m is mass , g is acc. due to gravity and h is height . Assuming ...
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When we write that $F = -\nabla V$ , what would happen if we ommit the (-) minus sign

I have had this question for a long time. In classical mechanics, if we choose $\mathbf F = -\mathbf \nabla \, V,$ with the minus sign, we can proof the work - kinetic energy theorem. What are the ...
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Work done changes between reference frames?

(This is not homework; a friend shared with me this puzzler and neither of us can figure it out.) Suppose you are in a plane traveling at velocity $v_1$ relative to the ground. The flight attendent ...
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Why work is a scalar and not a vector?

Work (in physics) is a scalar, but why? And why not a vector?
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Is my textbook teaching an incorrect concept of Work?

I fear my textbook is teaching an incorrect concept of Work. I am very frustrated right now since I was struggling to understand the concept in the way that was explained in the textbook and my ...
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342 views

Can infinite work be done?

Wikipedia defines work as follows. In physics, a force is said to do work if, when acting on a body, there is a displacement of the point of application in the direction of the force. Also work ...
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Is energy expended when a force is exerted on a object? [duplicate]

Energy is expended when a person exerts force on a object. 1) From the equation Work Done = Force x Distance, if a force is exerted, but no distance moved, then no work is done. Hence, the statement ...
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Why doesn't static friction decelerate a rolling body?

I know that static friction isn't the cause of deceleration of a rolling body. But if static friction is the only force in the horizontal direction, then shouldn't there be some acceleration produced ...
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How did Feynman prove that energy cannot be extracted from electric field?

In the Feynman Lectures, vol. II, chapter 4, Feynman discusses electric potential and says: If we carry a charge from point $a \to b$, $$W = -\int_{a}^{b} \mathbf{F} \cdot ds.$$ Now, in general, ...
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713 views

Validity of work-energy theorem in presence of non-conservative forces?

How can the work-energy theorem be valid in presence of non-conservative forces since conservation of energy is not there?
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Find work done by force along a path - is parameterization the only way?

$F = x^3y^4 \hat i + x^4y^3 \hat j$ from $(0,0)$ to $(1,1)$. I am given different paths. For example, "first along x axis and then along the y axis" is one of the paths. Is this problem solvable ...
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Confusion with $F=-\nabla V$, $F$ conservative

I am rather confused by the relationship $F=-\nabla V$. If a pen drops from a height it loses potential energy so $\nabla V$ is negative. From the above equation this means that the gravitational ...
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919 views

Problem in understanding the Proof of $PV^{\gamma}$ =constant in thermodynamics

I have looked at the proof of this relation $PV^\gamma = C$; (where $P$ is pressure and $V$ is volume) in quite some places but I am not able to understand the logic behind the third step. In ...
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454 views

What is the mathematical definition of work?

I'm looking for the pure mathematical definition of work, but I haven't yet learned line integrals. My book says that the work due to a force ${\bf F}$ from point $A$ to point $B$ is $$ W= |AB|\cdot ...
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139 views

The lab have a constant electric field and a constant magnetic field, what is the electric and magnetic field inside a conductor and far from it

The following is an old question from an exam in a Physics $2$ course I am taking, I have tried to solve the question and after I thought I got the answer I looked at the solution and saw it isn't ...
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1answer
72 views

Help understanding work

I have this problem: An object with 800kg mass is lifted up 2.4m by a force $F$. How much work does the Force do on the object (gravity is the only other force acting on the object)? From what ...
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1answer
72 views

What exactly is conservative vector field?

I'm studying calculus, but since the example involved a physical concept. I will ask here: This is how it goes: This means that in a conservative force field, the amount of work required to ...
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369 views

What is the meaning of the negative sign in $W = -\Delta U$?

What is the meaning of the negative sign in $W = -\Delta U$ ? As far as I understand, $W = -\Delta U = -(U_f - U_i) = U_i - U_f$. While $U_i$ is the initial potential energy (before applying the ...
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Understanding relationship between work and energy

I've read over 10 books about work and energy, and I just simply can't understand it. First of all, they go ahead and randomly define that work is force times distance: $$W=F X \cos\theta$$ Okay, ...
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871 views

Definition of force, kinetic energy and momentum

I've edited the post. Q1 and Q4 are the important ones but I didn't delete Q2 and Q3 since some older answers would not make sense anymore. To begin with, the formula of the kinetic energy $T$ is ...
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Work in circular motions

Suppose that a satellite circles around a planet that exerts $2000N$ of gravitational force on the satellite. I understand the fact that since the circular motion and the centripetal force are ...
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Work done by vibrating string

figure from http://webusers.physics.illinois.edu/~m-stone5/mma/notes/amaster.pdf The string has fixed ends, a mass per unit length of $\rho$, and is under tension $T$. This source claims that "the ...
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How to reconcile the two definitions of work? (mechanical and thermodynamical)

When studying classical mechanics, work is defined as: $W_M=\int F_{tot} \hspace{2 mm} dx$. However, for thermodynamics, work is defined as: $W_T=\int -F_{ext} \hspace{2 mm} dx$. I'm having trouble ...
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Work done by gravity on Water

Now according to me we would see change in potential energy of system and equate it to the work done by gravity. But when we see this the first column lowers by $H/2$ and right one rises by $H/2$ ...