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

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Why normal doesn't do any work in this case

Suppose the stick slides without friction along flat surface. Why in this case N does not do any work? As i see stick not only slides in horizontal direction, but also falls in vertical direction, ...
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1answer
56 views

Is work done in rolling friction?

I am confused by rolling friction. Suppose you have a cylinder rolling which starts at rest at the top of an incline plane and begins to roll down the plane without slipping. Is work done by the ...
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3answers
1k views

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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8answers
611 views

Energy and work

I don't quite understand the concept of energy and work. We can define energy as the ability to do work. An object moving at constant speed has kinetic energy. Does the object have the ability to do ...
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1answer
25 views

Work done by a homogeneous gravitational field on a system of particles

Perhaps this is trivial: how does one prove that the work done by a homogeneous gravitational field on a system of particles is equal to the work done on a point mass with the total mass of the ...
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3answers
66 views

Calculating work done on a rigid body

How in general does one calculate the work done by some force acting by a rigid body? Do you have to take into account the torque and the translation? For example: Suppose we have a ball rolling down ...
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1answer
78 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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3answers
189 views

Is work done = change in KE, or change in mechanical energy?

Starting from $F = ma$ we get: $$ F=m\frac{dv}{dt} = m\frac{ds}{dt}\frac{dv}{ds} = mv\frac{dv}{ds} $$ which leads to the work done: $$ W = \int Fds = \int mvdv = m\frac{v^2}{2} - m\frac{u^2}{2} ...
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1answer
42 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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2answers
73 views

Can magnetic force do work? [duplicate]

I have been told numerous times that magnetic force do no work at all but I have some trouble digesting this fact. Now suppose we have two straight wire with some current, they certainly can feel ...
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3answers
4k views

Is the normal force a conservative force?

Most of the time the normal force doesn't do any work because it's perpendicular to the direction of motion but if it does do work, would it be conservative or non-conservative? For example, consider ...
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1answer
32 views

An unwinding cable problem [closed]

Suppose a light cable is wrapped around a solid cylinder with mass $M$ and radius $R$. The cylinder rotates with no friction about a stationary horizontal axis. The free end of the cable is attached ...
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3answers
56 views

Do components of force have direction when doing work?

When we get angle > 0, the x-component of force is along the direction of displacement and so their product is called Work. So the x-component of force is said to have direction of the respective ...
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2answers
233 views

Difference between heat and work

According to the Kinetic Theory of Matter, temperature is nothing but a measure of the kinetic energy of matter. My textbook says that the change in internal energy of a system is the heat gained plus ...
2
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1answer
79 views

The work-energy theorem

Well here's the question. From some previous excercises we know that from \begin{align} A&=\int F\;ds,\\ &=\int ma\;ds, &&(F=ma)\\ &=\int m \frac{dv}{dt}\;ds, ...
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1answer
22 views

Do two engines with the same specific impulse always perform the same amount of work?

As the title say, do engines with different thrusts with the same $I_{sp}$ and the same amount of fuel perform the same amount of work?
2
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2answers
52 views

Another condition of calculating work

Let's imagine that there is a box placed at the corner of a table, and I push it so that my applied force makes an angle of 30° from the table's surface. The box would move and, due to the effect ...
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6answers
5k views

Does a magnetic field do work on an intrinsic magnetic dipole?

When you release a magnetic dipole in a nonuniform magnetic field, it will accelerate. I understand that for current loops (and other such macroscopic objects) the magnetic moment comes from moving ...
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1answer
51 views

What is the work done said when angle between force and displacement>90 and <180?

If the angle between $Force$ and $Displacement$ is obtuse then by using the formula of $Work$ we get negative quantity so is it said then that the system is losing energy or it is merely for the case ...
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7answers
3k views

Intuitively, how can the work done on an object be equal to zero?

To my understanding the work done on an object is defined mathematically as: $$W = \vec{F}\cdot\vec{S}=|\vec{F}||\vec{S}|cos\theta$$ This, I understand. My problem is that I don't understand that if ...
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3answers
288 views

A few questions about the concept of work

From Wikipedia: The work done by a constant force of magnitude F on a point that moves a displacement d in the direction of the force is the product: $$W = Fd.$$ If I lift some object from a ground, ...
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4answers
151 views

Work and its nature?

Suppose we have a constant force $\overrightarrow{F}$ and in the direction of force we have 2 point $x_1$ and $x_2$ in that order. And we have to calculate work done on moving frok $x_1$ to $x_2$ and ...
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1answer
79 views

Gravitational work

As far as I know gravitational work is independent from the path of the object, and I have an object that goes up on a inclined plane to a certain height, and than, after the object reaches the edge ...
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2answers
52 views

Factors on which Coefficient of restitution depend

What are the factors on which coefficient of restitution depend? What is the reason for more coefficient of restitution of two glass balls (0.95) than for two lead balls (0.20)?
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6answers
1k views

Why does a conservative force return the work done against it by a body to that body?

Newton's 3rd law of motion: Newton's third law of motion or the law of action and reaction implies that there is no isolated force in nature. Whenever there is any force at all , there must be ...
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2answers
184 views

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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4answers
88 views

What is the intuition behind “Net Work is Zero”?

I tried searching the answer to this all over the internet, but still cannot grasp this concept. So, when a book is being lifted, let's say $25 meters$ with a mass of $4kg$, with constant speed. I ...
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2answers
30 views

Does the effect change if a continuing and constant force acts upon a mass?

If a continuing and constant force $F$ acts upon a body with the mass $m$, does the power (work per unit time) increase over time? It would mean that the converted energy per time unit increases. Is ...
2
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3answers
108 views

The effect of windspeed on a car

I've worked problems in the past in trig class concerning the effect of wind on the speed of a plane and it's flight path and was wondering if a similar thing occurs with a car. First off, I'm ...
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2answers
110 views

Net work done for rubber bands

I know that work is done on a rubber band to extend it, and then the rubber band does work to contract. However, then what is the net work done? If it returns to its original length, is the area ...
7
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3answers
380 views

Why must a body lose energy to an opposing force?

A body must do work against an opposing force to continue motion. I have found this statement many times. But what is the reason behind it? Suppose $F_1$ is acting on a body to accelerate it (to ...
0
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0answers
47 views

Work done by heating a balloon with $H_2$ ideal gas

I have a difficulty treating this problem. Could you help me to understand the questions, please (I did my attempt)? Problem Consider a spherical balloon filled with $H_2$ gas. Due to a ...
10
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2answers
2k views

Calculating the force required to lift a weight with a screw

I am trying to learn physics by myself as I do not have a good teacher at school. I've been reading Feynman Lectures on Physics and I can't figure out how he found out this number. Here is an excerpt ...
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2answers
43 views

Finding the Work done

Find the work done for an object to slide down an inclined plane against the frictional force. The answer my book shows is : $$ W = mg ({\mu}_k \cos \theta - \sin \theta) S $$ where S = displacement ...
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3answers
2k views

How is it possible to equate the internal energy at constant volume with the internal energy of an adiabatic process?

I hope my question makes sense. My problem is that, I have read through numerous textbooks that $$nCdT = -PdV$$ (where $NC$ is constant volume) when deriving the relationship between $T$ and $V$ for ...
5
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1answer
216 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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3answers
81 views

Work done after explosion of chemical bomb

Question: Suppose, a chemical bomb is stationary. Then it explodes into n parts in all direction. What is work done? My Efforts The bomb is stationary, so momentum and and kinetic energy is 0. ...
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2answers
28 views

Understanding a graph of energy conservation with bounded and unbounded motions?

This graph is from the physics undergraduate text "Classical Mechanics by Douglas Gregory". Above this graph was the statement: What I didn't understand is- as stated in the under [*paragraph], ...
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0answers
31 views

Is work done on a fluid in a communicating vessel necessarily equal to work done by the fluid inside it?

During the explanation of Pascal's law the argument that work done by a force to move the fluid inside communicating vessel is equal to the work done by the fluid at the other end of the vessel was ...
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2answers
33 views

Work in electric potential

I've read that if we want to move a charge in an electric field then we need a work of an external force to move it from a low potential energy to a high one , but then I read on another source that ...
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2answers
106 views

Is the Fundamental Theorem of Calculus really applicable to the definition of work?

When the force $F$ on an object is not constant, then the work it performs is defined as $$W = \int_{x_0}^{x} F(X)dX.$$ Now, the Fundamental Theorem of Calculus states that $$\text{If}\,\,\, f(x) ...
5
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5answers
1k views

Kinetic energy vs. momentum?

As simple as this question might seem, I failed to intuitively answer it. Let's assume there is a $10,000$ $kg$ truck moving at $1$ $m/s$, so its momentum and KE are: $p=10,000$ $kg.m/s$ and ...
0
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0answers
23 views

Muscular energy transformations with regards to gravity

Maybe this has more to do with biology than I know, but I have been wondering just what kind of energy muscles use and convert when lifting a weight off the ground or lowering a weight back to the ...
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1answer
44 views

Derivation of a work done by forces on charge

Feynman claims is his lectures the following statement: Suppose we have two charges $q_1$ and $q_2$ separated by the distance $r_{12}$. There is some energy in the system, because a certain ...
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3answers
13k views

Thermodynamics - Sign convention

I use the sign convention: Heat absorbed by the system = $q+$ (positive) Heat evolved by the system = $q-$ (negative) Work done on the system = $w +$ (positive) Work done by the system = $w -$ ...
2
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2answers
74 views

Is the coefficient of restitution frame independent and energy conservation?

In this question I am ignoring relativistic effects. The following statements I think are true: change in Kinetic energy is not invariant under change of frame Force is invariant under change in ...
25
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4answers
2k views

The physical definition of work seems paradoxical

So this is possibly a misunderstanding of the meaning of work, but all the Physics texts, sites, and wiki that I've read don't clear this up for me: In the simplest case with the simplest statement, ...
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1answer
86 views

Magnitude of work

I am a little bit confused on the concept of work. By definition, work done by a constant force of magnitude F on a point that moves a displacement s in the direction of the force is W = Fs. So lets ...
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3answers
311 views

How was the definition and the formula of work derived? Is it the best possible?

Work done is defined as the dot product of force and displacement. However, intuitively, should it not be the product of force and the time for which the body is acted upon by the force (force * ...
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1answer
226 views

Acceleration of Center of Mass in Rotational Motion

I have a question regarding the acceleration of the center mass during rotational motion. From my understanding, Fnet = m*a(center of mass). Also, Torque = angular acceleration * moment of inertia. ...