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

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358 views

Is work energy theorem $W=\Delta K$ or $W=\Delta E$?

I know that work is the change in kinetic energy. I saw on an equation sheet that work is equal to the change in total energy. Is this true? If so, how?
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1answer
127 views

Find the velocity of water if power and mass is given [closed]

A pump of 200W power is lifting 2kg water from an average depth of 10m per second. Find the velocity of water delivered by the pump? $$P=200W$$ since the water is lifted per second ...
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1answer
65 views

Is there a special name for thermodynamic process during which no work is performed?

Let $W$ denote the work done on a system during a thermodynamic process. Is there a commonly-accepted, dedicated term for a process during which $W=0$?
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1answer
83 views

How do I found the Kinetic Energy of a mass being lifted?

I did an experiment where I lifted a mass and measured the force. I know the change in height, the mass, and the work of the pull. How can I use the work-kinetic energy theorem to find the final and ...
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2answers
126 views

Kinetic energy and work confusion [closed]

I know that $\frac{1}{2}mv^2$ is derived from $W = \int \vec F \cdot\ d\vec s$, but are there exceptions to the kinetic energy formula? Newton says that unless an external force is applied, a body ...
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2answers
84 views

Compression of spring when an object of given mass is placed on it

A question in my textbook says - A block of mass $m$ is released from rest onto an ideal non deformed spring from a negligible height. Neglecting air resistance, find compression $x$ of the spring. ...
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0answers
56 views

Electrostatic energy of a distribution of charges

I read, in Gettys' Physics, that, if $N$ charges moves one by one from infinity to a certain point, i.e. the first charge $q_1$ moves from infinity to the arrival point $P$ while the other charges ...
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2answers
49 views

Find $\oint xdx+2ydy+3zdz$ on the line segment formed by points $A(1,0,-1)$,$B(2,5,-1)$ [closed]

Find $\oint xdx+2ydy+3zdz$ on the line segment formed by points $A(1,0,-1)$,$B(2,5,-1)$ My approach: First I find the line segment formed by $A,B$ which is $\vec ...
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0answers
126 views

Ericsson cycle: what happens if you add more mass?

We recreated the Ericsson cycle using a heat engine apparatus, with air as the working fluid (assumed an ideal gas). During the isothermal compression and isobaric expansion processes, a mass of ...
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2answers
840 views

Work done by a non-conservative force and change in potential energy

I know that the work done by a non-conservative force is equal to the change in total mechanical energy (from Work-Energy Theorem). But I read in a place that "Non-conservative forces don't affect ...
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0answers
73 views

difference between reversible and irreversible entropy

Before I proceed, let me first say I have done research and understand the general idea between the two: summed up crudely reversible happens in a slower continuous manner while irreversible happens ...
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1answer
123 views

Clarify homework results regarding heat, work and the ideal gas law [closed]

So I have a bunch of homework problems relating to thermodynamics and work done by an ideal gas. I've been having trouble with the isobaric questions, and want to make sure I'm getting the concept ...
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1answer
94 views

What is meant by saying the work done by a conservative force is -(change in PE)?

I read through all related questions, and they are almost the same, but I still didn't understand this and so am asking again. What is meant when we say that the work done by conservative force is = ...
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1answer
134 views

Momentum and collisions [closed]

Two blocks of masses $m_1$ and $m_2$ connected by a spring of force constant $k$.The block $m_1$ is suddenly given a velocity $v_1$. Find the work done by the spring on both the blocks when it has ...
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1answer
252 views

Increase in kinetic energy of a system when there is no external force

If a man starts running on a boat with an acceleration $a$ with respect to the boat, there is no external force that acts on the Boat+Man system (assuming friction due to water to be zero and ...
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2answers
516 views

Positive work done by friction

Can work done by friction be positive? Please explain with an example. Is the work done by friction on a moving car positive?
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2answers
121 views

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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2answers
153 views

Work done by reaction forces between objects

Assume that there are no friction forces. If we had a particle sliding down a wedge that is free to move on a smooth surface, why do we ignore the work done by the reaction forces on both the particle ...
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0answers
56 views

Does Light have Weight?

If I light a torch and hold it against a wall, will the wall feel any force? If yes, what factors does the magnitude of such a force depend upon? (Area of the wall covered by the beam, intensity of ...
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1answer
66 views

Work done by tension when a particle is tied to a vertical cylinder using a thread and given a velocity perpendicular to the thread

For a particle attached to a rope moving along a circle that has the length of rope as radius, the tension provides centripetal force and work done by tension is zero since velocity of particle is ...
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4answers
415 views

Is work done by a pseudo force?

If a body is viewed from the frame of another body which is itself accelerating, will work be done by the pseudo force acting on the first body in the frame of second body ( provided the first body ...
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3answers
147 views

What was the motivation behind the work formula?

Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
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3answers
1k views

What is the relationship between entropy and work? [closed]

Can someone explain the relationship between entropy and work? I've been reading my textbook and looking online but I feel like I'm missing something. Can someone explain it in layman's terms :)
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5answers
148 views

Does work done require interaction between system and surrounding?

There's no work done for a person climbing upstairs because the energy is converted to PE within system only. The person is the system. How true is the above statement?
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3answers
246 views

Is there an intuitive explanation of the work formula?

Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
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3answers
298 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
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234 views

How to calculate the work of the electrostatic forces in a parallel-plate capacitor?

The expression of the energy stored in a parallel-plate capacitor is: $$U = \frac{e_0\cdot A \cdot V^2}{2d}$$ with $e_0$ the vacuum permittivity, $A$ the surface of the capacitor, $V$ the applied ...
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0answers
24 views

How does permanent magnets attract each other if the $B$-field can do no work? [duplicate]

How can two permanent magnets do work on each other? If you put two magnets with opposite poles facing each other they will attract each other. If you put them with the same poles facing each other ...
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0answers
109 views

The formula for calculating work transfer for a reversible adiabatic compression

Should we not be using Pdv for calculating the work done during a reversible adiabatic process ? Why are we using Vdp ? Can some one please explain this ? (P.S. I'm taking an introductory course on ...
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1answer
96 views

Usage of the formula Pdv for irreversible thermodynamic processes

Why do we use the formula Pdv for calculating work done in a irreversible process ? As per my knowledge , the term P indicates the pressure of the surrounding , which infinitesimally differs for the ...
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3answers
239 views

Work - constant or zero speed

Say I'm riding a bicycle at speed $v$. There's air that causes drag force, let's suppose it's constant, equal $F$, and it doesn't change with speed (we know it does increase quadratically with speed, ...
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1answer
38 views

How can I interpret $P(t) = \frac{1}{Q(t)} \frac{dW(t)}{dt}$ physically?

Generally speaking, one can calculate the work, $W$ (energy) required to compress a volume, $V$ of gas by integrating the pressure-volume 'loop' in a phase-space as $$W=\oint PdV$$ where $P$ is the ...
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2k views

Internal energy of an ideal gas as a function of volume

Okay so I've been reading a bit on Thermodynamics and I found something that I couldn't wrap around my head. For an ideal gas, the change in internal energy is equal to $$\Delta U = Q + W$$ And ...
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1answer
102 views

work and energy dilemma in an inclined [closed]

An example problem done in my book: A driver was driving a car of mass 1000 kg through an inclined plane which makes an angle of 30° with plane with a velocity of 25 m/s . Then he saw a boy 50 m ...
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1answer
99 views

Acceleration orthogonal to movement direction

I've been told that acceleration orthogonal to an objects movement direction doesn't require energy. Thus when a satellite goes around the earth, the change in direction caused by gravity doesn't use ...
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1answer
69 views

How is the kinetic energy of an object in collision converted to work done in deforming itself?

Usually, in a perfectly inelastic collision, maximum amount of KE is lost. I guess it depends on the rigidity of that object collision if any KE at all will be converted to work done to deform. ...
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1answer
191 views

How is power of a water pump related to amount of water delivered from pipe?

My book says: Suppose a pump motor is used to deliver water at a certain rate from a given pipe. To get n times the water from same pipe in same time the power must be increased by $n^3$ ...
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3answers
320 views

Infinite acceleration

Let's say we have two planets at a stand still within reasonable distance of each other. They will accelerate towards each other and subsequently collide. If instead we give them a sufficient (but ...
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3answers
161 views

How is Work by a System Interpretated in the First Law?

Good evening. I've happened to be sitting down today and just couldn't wrap my head around this question which seems rather simple at first. From reading about the first law and sign conventions as it ...
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1answer
78 views

How can we account for a friction force changing sign in a conservation of energy equation?

I want to solve a simple mechanical problem whereby three forces act upon an object. $F_1 = (10 - x)$ N $F_2 = -3 N$ (friction force) $F_3 = -10x$ N So at $x$ = 0 we see that $F_1$ + $F_2$ + $F_3$ ...
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1answer
105 views

Virtual work (generalized forces) for rotation with Euler angles

Here is what we know from virtual work: \begin{equation} \delta W=\sum_{i=1}^N{\vec F_i\cdot\delta\vec r_{i}} \end{equation} Where $N$ is the number of bodies in the system. I am considering a ...
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2answers
107 views

When is work done on or by something?

An example, here what my textbook says: When charges are released In electric fields charges experience the force causing them to accelerate along electric field vectors. Positive charges ...
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2answers
129 views

What is the work done?

A painter uses 1.93kJ of mechanical energy to pull on the rope and lift a 20kg paint barrel at constant speed to a height of 7.5m above the ground. How much work was done lifting the paint barrel? ...
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177 views

Is work-kinetic energy theorem useless?

This is how my book explains it: $W_{net} = \delta K$ Since the net work is tied to changes in kinetic energy and changes in speed, a mass must accelerate in order for net work to be nonzero. ...
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5answers
257 views

What exactly is work?

What exactly is work? My book confuses me: a force can lift an object to a height h, or it can accelerate an object through gravity. In all these cases, a force displaces an object and change the ...
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1answer
103 views

Work done by friction on a ball flying through air [closed]

A baseball of mass 145 g leaves a pitcher’s hand at 150km/hr, but due to constant air resistance, it arrives at home plate 20.0m away traveling at 145km/hr Assume that the magnitude of the ball’s ...
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1answer
82 views

Net work done by projectiles?

When the projectile is in motion what is the net work done on projectiles? What i think? 0 first view: We know when we throw projectiles the initial KE and final KE is 0. So from work energy ...
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3answers
165 views

How does The work done in going around any path in a gravitational field is zero implies conservation of energy?

In The Feynman Lectures, Feynman states: The work done in going around any path in a gravitational field is zero. This is a very remarkable result. It tells us something we did not previously ...
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1answer
33 views

Can the energy/power required to mix two fluids together be calculated?

Given two fluids; say for example oxygen and nitrogen gases. By simply introducing, again for example 1 liter of each gas into a closed container, the process of diffusion alone will eventually cause ...