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

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How do forces affect work? [closed]

I was doing my homework and I came across the question: Suppose that two objects, each with the same mass, are accelerated from rest to the same velocity. The force that accelerates one object ...
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1answer
52 views

Is it possible to ascend (or descend) an escalator, without consuming any more power produced by the motor of the escalator?

Is it possible to ascend (or descend) an escalator (which ascends with a constant speed), without consuming any more power (energy) produced by the motor of the escalator ? I mean, find a way to walk ...
2
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1answer
84 views

Why is friction not dissipative in rolling motion? [duplicate]

We know that non-conservative forces like friction is a dissipative force. But according to my book when a solid cylinder is rolling down a rough inclined plane of inclination angle $\theta$ the ...
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1answer
89 views

Question about solving a problem using Newton's Laws and work and energy [closed]

The question is this: Darla pushes a $5.0kg$ crate up a $2.0m$ high $20^o$ frictionless slope by pushing it with a constant horizontal force of $25N$. What is the speed of the crate as it reaches ...
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3answers
500 views

Why is walking up stairs harder than walking normally?

I must admit, I'm pretty new to studying physics and I know this is a simple concept but I'm having difficulty understanding it. I've tried reading the questions here but I just need a little bit of ...
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3answers
165 views

Does the work done by a person equal the work done on the object in this situation?

If you applied a constant force over a floor that has friction on an object, would the work done by the person equal to the work done on the object? Assume that the floor is flat and that the object ...
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1answer
71 views

Properly deriving the formula for the kinetic energy

I am a physics student and recently attended my first lectures. One thing that strikes me even now was the way the professor derived the formula for the kinetic energy. He started with the (already ...
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3answers
111 views

What's the work done by a spring on a block when it moves from extreme to mean position?

I really don't know where am I doing it wrong, but block when it moves towards mean position displacement will be along the force right, so the force acting on block will be $+fxdx$ Integrating we ...
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2answers
130 views

Is work a form of energy or means of transfer of energy? [duplicate]

What actually is energy? Is it a property associated with matter or just a number? By doing work are we changing the energy of the body or converting one form of energy into other which is already ...
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2answers
44 views

Phsyics Energy Problem + Concept

A simple problem really. Part 1 Suppose a ball ($20. ~kg$) was shot straight up with an initial velocity of $+50~m/s$. a. Assuming that all of the ball's initial $E_k$ was transformed into $...
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2answers
58 views

I have trouble understanding work

I am just starting out in physics. I study in germany, so excuse me if I get some terms wrong. I am trying to understand why 'Work = Force * Way' and I think I just have some trouble imagining what ...
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1answer
61 views

A question about thermodynamic reversible process [closed]

I am a new learner of thermodynamics, and I have a question in my assignment: Show that $W$ and $Q$ for an arbitraty mechanically reversible nonflow process are given by: $$W=\int VdP - \Delta(...
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1answer
45 views

Calculation of Work

Typically I see problems laid out along these lines. If you are lifting a 100 kg weight 1 meter how much work do you do? Work = Force * Distance Work = (100 kg) (9.8 m/s^2) * 1 m = 980 J But it ...
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2answers
55 views

Finding the work done to fill the tank by pumping water over the edge? [closed]

I am really confused on how to approach the following question and how to set it up. So the question is: An open tank has the shape of a frustrum of a right circular cone. The tank is $4\:\mathrm{...
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2answers
49 views

Where does the energy required to speed the object in this question come from if the object actually slows down from another perspective?

I was thinking about mechanics and energy and stumped myself with this scenario I made up: Suppose you are in a room and you are motionless. In the same room, a 1 Kg ball is moving to your right with ...
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1answer
60 views

Why is a satellite's GPE negative? [duplicate]

Okay, so the formula for Gravitational Potential Energy (GPE) of satellites is: $$ U=-GmM/d$$ Mass and distance can't be negative, and $G$ is constant that is not negative. Why is a satellite's GPE ...
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2answers
120 views

The work done by a spring over a specific distance

I cannot seem to find the answer for my question. I know that the formula for work is $W = FD$. Given a mass that is attached to unstretched spring and is pushed by some force to stretch the spring, ...
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3answers
254 views

Why does the work-energy theorem need to include internal forces?

Can anyone kindly explain me why work energy theorem must also include internal forces? The proof of work energy theorem is derived from Newton's laws of motion, but Newton's laws of motion don't ...
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1answer
64 views

Work done should be positive but it is coming out to be negative? [closed]

I have described a question in which this problem arises in the image below:
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2answers
121 views

Can a glider maintain a constant forward velocity component?

I have a puzzle which asks me to consider a (engineless) glider descending at a constant rate and flying at a constant forward velocity (in still air). The question asks how to derive sink rate, $v_s =...
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1answer
32 views

Work done when applying an electric field?

On these example questions from MIT in the solution to 4.1 they write the work done by applying the electric field to be: $$W=V_0 \int \vec E \cdot d \vec D$$ Where does this equation come from and ...
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1answer
86 views

Work done by friction opposing a force at an angle

Let's imagine there's a block of mass m sitting on a rough surface with a kinetic friction coefficient $\mu$. It's being pulled with a constant force $A$ at $h$ degrees above the horizontal and is ...
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3answers
2k views

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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1answer
40 views

Heat, Work and Internal energy in closed systems

This has been troubling me for a while now. I know that the performed work equals $P\Delta V$ for isobaric systems and I know that in isochoric systems no work is done, but how do I find the heat $Q$? ...
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1answer
86 views

Work done by gravitational force!

Suppose a ball is $10m$ high from the ground. It will have $E_p = 10mg$. Now, if the ball falls freely then we know $E_k$ will be $0.5mv^2 = E_p$. But it is said that the work done by a force will ...
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164 views

Work done against gravity comes out positive

Given two points in 3-space, $A = (9, 1, 5)$ and $B=(2,8,7)$, the work done by the gravitational field $\bf{F}$ when an object is moved from point $A$ to point $B$ comes out positive, even though it ...
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3answers
985 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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4answers
348 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 ...
2
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1answer
344 views

Electric field for concentric spheres

I have a couple clarifying questions: (A) in $E=kq/r^2$ for the area between a sphere inside another spherical shell, the sphere inside is considered a point charge. However, the sphere inside has a ...
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1answer
146 views

How are the watt-second, the newton-meter and the joule different?

The joule is $\mathrm{kg\,\ m^2/s^2}$ right? The watt-second is $\mathrm{J/s} \times \mathrm{s}$ thus $\mathrm{J}$. The newton-meter is $\mathrm{kg \,\ m/s^2} \times \mathrm{m}$ thus $\mathrm{kg \,\ ...
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2answers
584 views

Change in internal energy is 0 in isothermal process

I am having trouble understanding why in an isothermal process, the change in internal energy is zero. I know that $\Delta U$ or $\Delta E=q+w$, and so in isothermal process $q=0$. But how does one ...
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1answer
53 views

Work and energy question

An athlete picks up a $20.0\,\mathrm{kg}$ sandbag from the ground and throws t straight up in the air. It leaves her hands $1.50\,\mathrm{m}$ above the ground and reaches a height of $7.00\,\mathrm{m}$...
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2answers
90 views

Why isn't the work minus the potential energy when bringing a charge in from infinity?

This is an example in my physics textbook, and there is just one step that I don't understand. Two point charges are located on the x-axis, $q_1 = -e$ at $x = 0$ and $q_2 = +e$ at $x=a$. Find ...
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2answers
150 views

Can I define the term energy in terms of work?

Recently, I'm doing my personal task which is to formalize every definition and concept in physics, by means of formal language and of course with intuitional notes. Because I found myself that the ...
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3answers
145 views

Work done by a constant vector field is 0?

We know that $$\oint \boldsymbol{F}\cdot d\boldsymbol{r}= \iint (\nabla \times \boldsymbol{F})\cdot d\boldsymbol{s}.$$ Now if $\boldsymbol{F}$ is a constant vector, then $\nabla \times \boldsymbol{F}=...
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1answer
416 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
144 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 $$W=\frac{P}{1s}=...
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1answer
66 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
92 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
132 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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3answers
112 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
52 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 l(t)=\vec{OA}+t\vec{AB}=(1,0,-1)+t(1,...
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0answers
147 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 ...
2
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2answers
929 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 PE"....
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0answers
76 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
129 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 ...
0
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1answer
95 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
142 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 ...