Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [work]

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

-2
votes
1answer
39 views

Uniform Circular Motion and Work [on hold]

I was usually told that in a uniform circular motion the work is 0 because the force is every instant perpendicular to the displacement. However, studying the motion i noticed that there is a force ...
0
votes
1answer
29 views

Pumping fluid out of a tank: how does intake location affect work?

I was working a calculus II problem on the board, teaching how to solve the fluid pumping problems. I drew a tube from the top of the container to the bottom, and a student asked about how that ...
0
votes
1answer
39 views

Is it possible that the particles can be brought by some external agency without changing the kinetic energy? [duplicate]

I am a student and I've been studying a physics book. There is one statement in the solution of one question (regarding calculation of Potential energy) which is confusing me. It states that: If ...
0
votes
1answer
61 views

Factor $1/2$ in work done by spring force [duplicate]

My book says Spring Force = $-kx$ where k is spring constant and x is displacement from equilibrium position. Then it says work done by spring force is $-kx^2/2$. But I know Work Done = Force $×$ ...
-2
votes
2answers
52 views

Understanding relation between work and energy

Consider you are travelling on a board in the space moving with 5m/s velocity. There is no force acting on it. Now consider you have 2 stones of 1kg in your hand. So the stones also had 5m/s velocity. ...
26
votes
3answers
2k views

Why is the work done by a rocket engine greater at higher speeds? [duplicate]

From this comment by orlp: If I strap a rocket booster to a rocket in space and fire it for one second, then the work provided is much higher when the rocket is flying fast compared to when the ...
-3
votes
0answers
25 views

Kinematics Using Energy [closed]

A ball is thrown up vertically from the ground at an initial speed of $u$. Neglecting the effects of resistance, find the final speed $v$ of the object when it is at height $h$ above the ground. My ...
24
votes
9answers
5k views

Why does work depend on distance?

So the formula for work is$$ \left[\text{work}\right] ~=~ \left[\text{force}\right] \, \times \, \left[\text{distance}\right] \,. $$ I'm trying to get an understanding of how this represents energy. ...
1
vote
4answers
75 views

Why does force x distance not equal kinetic energy for objects rolling down an inclined plane?

Imagine two objects at rest at the top of an inclined plane which are capable of rolling and which are identical in every way (mass, radius, etc) with the exception of how their mass is distributed. ...
0
votes
2answers
81 views

Mass moving at a constant velocity vertically

Let's say I move a mass of 10kg up by 1m at a constant velocity. I would have done 10J of work on it, and gravity would have done -10J of work. However, wouldn't that imply that the net work done is ...
7
votes
3answers
68 views

What is the differentiating factor between work and heat?'

Although work and heat do the same thing (increase or decrease the internal energy of the system), There is still a fundamental difference between them. For example, The way in which entropy is ...
2
votes
1answer
24 views

If magnetic induction vector will not be perpendicular to charge velocity, there will be work?

The work is $A=FS$ The force is $F=q[E+v\times B]$ The $v \times B$ is a new vector, $|v||B|\sin\space \alpha$ Let's consider the next case: Where red dot is a particle, moving due to $v$. We do ...
1
vote
2answers
36 views

Force, work and the apparent disappearance of Mechanical Energy [duplicate]

A man exerts force on a wall of bricks. The man must have consumed the energy he possessed (mechanical energy?) to exert the force. The man sweats and tires himself out but the wall does not move. ...
-2
votes
1answer
31 views

Forces From Opposite Sides On A Block

Suppose we have an indestructible box in space , and we apply equal forces on two opposite side of box , the box wont move but then where will the energy go?(Conservation of energy)
-1
votes
1answer
58 views

Work done by moving a body moving on a circular path [closed]

A body moving in circular path of radius $8\sqrt{2}m$ is acted upon by force: $-y\hat i +x\hat j$. Find work done by its complete revolution. So I was trying this question and I could solve it in ...
2
votes
0answers
46 views

Constraint forces do no virtual work: does this always apply?

The thread title is my main question, but to give some context, I'll include a particular example that made me ask the question in the first place. In Hand and Finch, a small block is on a ...
0
votes
3answers
61 views

Work done by pulling yourself up a platform

I am struggling with the following problem: A platform has a rope attached to it which extends vertically upward, over a pulley, and then back down. You stand on the platform. The combined mass of ...
0
votes
3answers
96 views

Exergy, entropy and energy quality

I'm teaching a class on the subject of "energy quality". I'm supposed to tell them that energy quality is a measure of how easily (effective I guess) the type of energy can be converted to different ...
0
votes
1answer
47 views

Different types of mechanic jacks [closed]

I need help. I would like to know: what the differences between the jacks illustrated below are and with which jack a car can be lifted easiest (according to the answer sheet it is jack **B).** My ...
0
votes
3answers
59 views

When talking about potential difference in a circuit, whose work done are we talking about?

I'm asking this because it seems to me that when we talk about PD around a charge (i.e. potential difference between infinity and a point), we're talking about the work done per unit charge by an ...
5
votes
3answers
89 views

Why exactly is work a path function?

This might be a stupid question, but why exactly is work a path function? In school, my teacher said it’s because it depends on the path. She gave an example of walking up a mountain, and said the ...
0
votes
1answer
81 views

Adiabatic closed system work

The closed system work PdV is path dependent but it is path independent for an adiabatic process as can be shown by applying conservation of energy on a closed system (dQ = dE + PdV),here dE is change ...
0
votes
1answer
43 views

Total work zero along the virtual displacement

I'm having some trouble understanding virtual work and displacement, especially a particular section of Goldstein. I'll use an example to explain my difficulty, but I realize this might be the product ...
-1
votes
2answers
53 views

Why can work done by friction be negative if work is a scalar?

Work done by an object can be defined as the force times the distance traveled in the direction of the force. I've read from the internet that the frictional force acting on an object sliding over a ...
3
votes
2answers
55 views

Why does exerting force sometimes cost energy and sometimes not?

Inspired by these similar questions, which have some very good answer to what they are, but they all focus on what is happening. None of them explains why it only applies sometimes and not others. I'...
-1
votes
1answer
55 views

What is the difference between Kinetic energy and Work? [closed]

Can we say that the work is the difference in the energy of motion
0
votes
1answer
29 views

Difference in work done for different directions of motion [closed]

If I am lifting a weight, i.e, a rectangular object of 200kgs from one end off the ground(around 3 inches above the ground) having a dimension of 48 inches by 30 inches. How much weight am I lifting ...
3
votes
2answers
85 views

Work of normal force

I've had an interesting conversation a day ago and we came to a stop regarding one explanation. Conversation went about how increasing brake rotors doesn't make your car stop faster. But we came to ...
1
vote
4answers
62 views

Confusion on work done by an ideal gas

When an ideal gas,in a piston kind of system and whose equilibrium state is mentioned, is allowed to expand (piston is allowed to move and not gas leaking )against a constant external pressure very ...
0
votes
1answer
57 views

Potential potential?

I'm a noob trying to understand concepts before details (which itself could be a mistake cuz I think my head is about to explode) A big part of my difficulty is terms - they are blocking my conceptual ...
0
votes
3answers
17 views

Work in relation to introducing a positively charged object into a positively charged sphere

A text I am reading claims that when one introduces a small positively charged ball (B) into a positively charged metallic sphere (A) (through a tiny hole, with a thread), one performs work. This then ...
2
votes
3answers
27 views

The work-energy principle for particles reversing direction

I've been trying to find an answer to this question, but have really been stumped so far. The work-energy principle says that work done on a single particle is equal to its change in kinetic energy. ...
0
votes
3answers
38 views

Why is the gravitational potential energy (or electrical) the work done to move a point mass $m$ from infinity to that point in a gravitational field?

To be specific, I'm asking why does the mass need to be moved "at a constant speed"? My textbook says it is so that no kinetic energy is involved. But shouldn't kinetic energy be involved in order ...
1
vote
0answers
48 views

Confusion on work done in reversible and irreversible process and others

I am greatly confused with the following things Work done in reversible and irreversible process Here: Since first law is only the energy conservation, if you have a gas, closed with a movable ...
-1
votes
0answers
12 views

What happens energy-wise when lifting a weight while standing still? [duplicate]

When lifting an object and keeping it at a certain height, it is clear that I'm exerting on the object an upward force that is opposite to its own weight, as the overall situation is static. However,...
0
votes
0answers
30 views

Thermodynamic 'Work Flow'; Based on relative or absolute pressure?

The thermodynamic work flow (energy) is defined as $$W = \int PdV = \int PQdt$$ The units of $P$ are the same whether $P$ is considered relative (gauge) or absolute pressure. But then what should $...
0
votes
0answers
30 views

Question about Work performed between two points within an electric field

In an exercise in my Physics Textbook, I was asked to calculate the amount of Work necessary to move a charge of -$1.6\cdot10^{-6}$ Coulomb from P to R, and from R to O (see attached picture below). ...
0
votes
2answers
29 views

Energy conservation in a balloon

If a helium balloon moves up with a net acceleration a then does its potential and kinetic energies increase simultaneously?
0
votes
1answer
56 views

Integral of a force

I have what is probably quite a basic question: A block of mass 5 kg is subject to a force $\ F = 3x + 5x^2 $ (in N). The block is initially at rest at $\ x = 1$. Its speed when $\ x = 5$ is: ...
0
votes
1answer
32 views

feynman shell theorem

I understand the general derivation of the shell theorem by feynman but I don't get why he denotes the potential energy with W, the symbol for work. I would understand this if they would be the same ...
0
votes
3answers
28 views

Potential energy and work-energy theorem

Let us suppose that a ball is present on earth's surface, gravity acts on it. Now if a force is applied on the ball in the opposite direction of gravity such that the applied force counters gravity ...
1
vote
3answers
170 views

Is gravitational energy always conserved?

If I take a body to a height $h$ then I did the work $mgh$, but gravity does the work of $-mgh$, so the net work done would be 0. So why do we say that at that height $h$ the body will have potential ...
1
vote
1answer
65 views

Why does taking work from a system not reduce its entropy?

In Daniel Schroeder's book Thermal Physics, he makes the point that as energy is put into a system it's entropy goes up (there are some exceptions to this generally, but for this question we can ...
0
votes
3answers
108 views

Kinetic energy and conservative fields

If $W = E_1 - E_0$ for every force and a conservative field is a field such that the work on a closed path is 0, then every field should be conservative, since $W = E_0 - E_0 = 0$. I know that this ...
1
vote
1answer
40 views

Does measured mechanical power and work change between inertial frames?

Imagine a car A is accelerating. Two observers at constant speed, B and C, analyse the change of A's kinetic energy over a same time interval. B sees A going from 10 to 30 m/s C sees A going from ...
2
votes
0answers
25 views

Work done in force field

I have a force $$\vec{F}=x^2 z \hat{i}+3y^3 \hat{j} +xz \hat{k}$$ which can readily be seen to be non-conservative. I want to compute the work done moving a particle of unit mass from point $(1,0,\...
1
vote
2answers
57 views

Discrepancy in general work and pressure-volume work

Consider a massless, frictionless piston fit into an airtight container containing an ideal gas. And let us say that the gas undergoes quasi-static isothermal expansion by lowering the pressure ...
1
vote
3answers
58 views

Internal and external forces

When a person lifts a book while standing on the earth's surface. Why is his force considered external to the book-earth system? Isn't his force internal like the case of the forces that cause the ...
-1
votes
1answer
34 views

Spring-Block system [closed]

Here is a multiple spring and a block system. I need to find the maximum elongation of the spring. I tried to take $mg-(k_1+k_2)x=0$, and find $x$ from there. The answer is coming wrong. It should ...
0
votes
2answers
49 views

If efficiency is more important, then why condenser is used in boiler?

What's the real reason behind condenser? some says, Without condenser, back-pressure will be created in turbine. After Expansion in turbine, entropy will be maximum so it must be cooled to reduce ...