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.

0
votes
4answers
83 views

How did we come up with the formula of the work done by a force? [duplicate]

I don't understand why the work represent the change in energy of a system. I understand the work energy theorem but where did we get the formula of the work from in the first place. Also when I ...
0
votes
1answer
39 views

Doubt in thermodynamics pressure volume work done

Why work done in irreversible process is not calculated as -$\int p_{internal} dV$ ?
1
vote
2answers
50 views

Work done by friction when object is rolling WITH slipping

So if I have an object that is rolling with slipping like a bowling ball, if I use W=F•dr definition, then work done by friction has to be negative. But if I use the W=τ•dθ definition, then work is ...
0
votes
0answers
27 views

Relationship between work and kinetic energy?

Lab Question: What is the relationship between the work done on a car as it rolls down a ramp and its kinetic energy at the bottom of the ramp? We have a 30 gram car that starts above a table and ...
1
vote
2answers
49 views

how can internal energy do work?

how can internal energy do work? As far as i know, internal energy is the sum of KE and PE. But how can this, in turn, do work? It would be great if you can give me some scenarios. Thank you.
-1
votes
1answer
37 views

How does thermal energy in a system do mechanical work? [on hold]

Explain that a system with thermal energy has the capacity to do mechanical work. Also, in addition to this what are the differences between work and mechanical work?
0
votes
4answers
39 views

Why does the GPE of an object always equal the work done?

I had a question that said, "If you do 100 J of work to lift an object over your head, what is the gravitational potential energy relative to its starting position? What would be its gravitational ...
2
votes
5answers
47 views

Work done in lifting a mass vs work done by mass as it falls to starting position

There are variations of this question on here but I was unable to find exactly what I was looking for so please bear with me if this is old hat. If I start with a mass m at rest at height H1 and ...
0
votes
0answers
40 views

Maximum achievable mechanical work when heating water

I am doing a question about finding maximum achievable mechanical work when 1L of liquid water is heated from T₁ to T₂ at atmospheric pressure. The solution is $$W = \int_{T_1}^{T_2} \frac{T - T_1}{T} ...
0
votes
0answers
20 views

If is work done by magnetic field is 0 then why does 2 magnets attract when kept together? [duplicate]

If 2 magnets are kept close to each other they attract then shouldn't it be considered as work done by magnetic field?
0
votes
3answers
51 views

Does potential energy get transferred from my body to a wall when I push a wall and fail to move it?

When I push a rock (and fail to move it), I do not do any work and therefore there should be no energy transfer. But my teacher says that, when one pushes a rock, energy is transferred to the rock ...
3
votes
2answers
73 views

Work extracted from a pressure cooker

How much work can you extract from a turbine connected to a pressure cooker? The situation is modeled as a rigid adiabatic tank of volume $V_{tank}$, which initially contains water at a high ...
0
votes
4answers
86 views

Why do we use heat engines if they are so inefficient?

Let's say I wish to build an engine which will launch a box vertically upwards. I propose two such engine designs: Engine 1 (finger, spring, box) Step 1: Orient uncompressed spring vertically. ...
0
votes
1answer
54 views

Why is work done by the system in a Carnot engine?

In a Carnot engine, represented above, it is said that work is done by the system, but in reality , work is done by the system only in the isothermal and adiabatic expansions (from 1 to 3 in the ...
-1
votes
5answers
75 views

Why does a point mass make a certain angle with a force exerted on it?

In real world, I see that if I hit (physicall speaking exert a force on)a marble or billiard ball properly (I think in its center of mass) it goes in a straight line with the force which means the ...
0
votes
2answers
35 views

Why isn't the work done on the spring encapsulating this idea?

We know that work done ON the spring is given by the integral $$\int kx \, dx =\frac12kx^2$$ if we start from $x=0$ .But what if I apply more force on the spring.Wouldn't I be doing more work on it? ...
0
votes
2answers
52 views

Why the work done on the spring is different?

If a Woman weighing $600 N$ steps on a bathroom scale containing a stiff spring, the spring is compressed $1.0 cm$ under her weight, the spring constant is $60000 N/m$.It turns out that the work done ...
0
votes
1answer
57 views

Negative Work done by gravity

When we lift an object from ground we say we did work on object . We also say that gravity has done negative work because we did work to overcome gravity . When we did work our chemical energy was ...
0
votes
1answer
38 views

I am having trouble understanding work and the factor of time

Consider this: 1 kg object vs 1000 kg object No friction applies in my example and the machine I am using is 100% efficient. Some machine using a fuel applies 1 N of force over 1 meter to each object ...
0
votes
2answers
47 views

Why does not the static friction produce heat and waste energy?

I have asked this question wrt this question. So I want to ask the static friction opposing not the motion of the field just helps the field to get the energy back so the work now why does not the ...
-1
votes
1answer
36 views

Finding the drag force from the final velocity of a falling object

I know the velocities (v) of an object after it fell for respective distances (s). From that alone, is it possible to calculate the drag force at a specific moment in time? If not what else would I ...
1
vote
1answer
69 views

Where does the heat energy dissipated by friction come from?

I know that when a force is exerted on an object by another one which causes it to move, work is performed. As a result energy is transferred to the object by the force from other object. But ...
1
vote
2answers
65 views

Work done by friction in this Case

So there is an elevator going down with a constant and the block does not slip on the wedge. We have to find the work done by friction in time t. So the answer given is $-mgvt\sin^2\theta$. What I ...
0
votes
0answers
43 views

The maximum work theorem for different reversible processes

Citing the Callen thermodynamics book (page 105): "for all processes leading from the specified initial state to the specified final state of the primary system, the delivery of work is maximum for a ...
2
votes
6answers
101 views

Potential Energy and Work [duplicate]

My physics textbook says when a rock is lifted gravity does negative work and increases the gravitational potential energy. My understanding of negative work implies energy is being removed when an ...
0
votes
2answers
49 views

Inconsistency in the definition of electrostatic work

Sorry if there this is a duplicate but I can't find anything that deals with this. I have a point charge $q$ sitting at the origin. It takes no work for me to put it there. Then, I bring $-q$ out ...
1
vote
1answer
35 views

Irreversible and reversible compression work

Why is work done on the gas when it is compressed from (p2,V2) (pressure,volume) to (p1,V1) against constant pressure external pressure p1 maximum when it is done irreversibly? In reversible process, ...
0
votes
3answers
121 views

If a satellite moves towards Earth, is negative work done against the force of gravity?

A bit confused here - if a satellite approaches Earth, its displacement is in the same direction as the gravitational force (towards the centre of rotation). Therefore, gravity is doing positive work? ...
0
votes
1answer
30 views

Formula for Power from Kinetic Energy

Work Done = $Fd$ Power = $Fv$ If the (net) Work Done = Change in Kinetic Energy, and the object starts from rest: Work Done = $\frac{1}{2} mv^2$ Power = $\frac{1}{2} m av$ Power = $\frac{1}{2} ...
-3
votes
0answers
39 views

Is angular momentum , energy? [duplicate]

is angular momentum energy? I mean why is the unit of torque N CROSS m and it is not considered energy but the unite of angular momentum is j.s?
1
vote
3answers
54 views

How are various forms of energy ability to do work? [closed]

According to various sources that i have come across, energy is the ability to do work. Can someone elaborate how diff forms of energy like potential energy and kinetic energy are ability to do work? ...
-1
votes
1answer
40 views

How calculate work from an electric field on a $+q$ particle without the curve? [closed]

Well,i've a workout for home,and it is asking me to calculate the work from the electric field with equation: $\hat E=6xy \hat x+(3x^2-y^2)\hat y$ I tried to solve the line integral but it doesn't ...
-1
votes
2answers
68 views

Why is work defined with respect to distance rather than time? [duplicate]

The common way of finding the work done on some object is by applying the equation: force*displacement. However, suppose we apply a force of F newtons on an object of mass M for a duration of T ...
0
votes
1answer
68 views

Work done in accelerating an object in circular motion

In a hammer throw competition, an athlete spins a “hammer” before releasing it. The “hammer” used in this sport is a metal ball of mass 𝑀 = 8 kg and diameter 𝐷 = 30cm, which is attached to a ...
0
votes
3answers
93 views

How can we define energy other than the definition that it's a capability to do work? [closed]

It is actually a property of energy that it can do some work not an actual mean to define it because we cannot define a thing on the basis of what it is doing or what it can do.
0
votes
1answer
107 views

If irreversible process is quasistatic then can we find it's work using $pdv$ formula?

Now it's given on Wikipedia that quasistatic process can be irreversible,so can I find the work done by the closed system undergoing a process using $pdv$ work?...Next, is that work less than the ...
1
vote
1answer
44 views

Negative work done by dark energy

If I lift a book up, I applied a force opposite its weight so there's positive work done. Dark energy is said to be pushing galaxies apart and the energy is coming from this negative work done. ...
0
votes
0answers
26 views

Why an elementary work is written $\delta W$ instead of $dW$? [duplicate]

Why an elementary work is written $\delta W$ instead of $dW$? For example, it's often written $$\delta W=F\cdot dr$$ if $dr$ is the elementary displacement. Why don't we write as usual $dW=F\cdot dr$?
0
votes
2answers
57 views

How to calculate work for irreversible adiabatic processes?

By the first law, we know $\text{d}U=\delta Q+\delta W$ and, on adiabats, we know $\text{d} U=\delta W$. But what is $\delta W$ for irreversible adiabatic processes? Take a thermally isolated ...
1
vote
2answers
33 views

How to study the work done by a varying force on a system moving in two dimensions?

My book states that: $$W=\int_{x_i}^{x_f}{F_x dx}$$ We can calculate the area under the curve representing force as a function of position when the displacement and the force are in one direction ...
1
vote
2answers
76 views

Work definition does not make any sense for coherent states? TPM (two projective measurement) scheme

I'm talking about the relation that if we are in a isolated, quantum system that only allows for work exchange with the surrounding system we know from the first law of thermodynamics that $\Delta E = ...
-1
votes
2answers
25 views

Proof for $W_{\text{total}}$

Looking upon a certain solution of a problem in Griffiths regarding the work done in arranging two concentric spheres with inner shell having charge $q$ and outer shell with charge $-q$ and I found a ...
4
votes
4answers
349 views

Can potential energy be the sum of the work done by all forces?

I often see that the total energy of a system is the sum of potential energy+ kinetic energy. Is it always like that? Could I say that the total energy of a system is the sum of the work of all force +...
0
votes
1answer
36 views

Why the work of the weight of the pendulum is $mg\cos \theta \ell$?

Why the work of the weight of a pendulum is $mg\ell\cos \theta $? Consider the coordinate system $(O,e_r,e_\theta )$. Then $P=(mg\cos\theta ,mg\sin \theta )$, and thus $$\delta W_P= P\cdot dr.$$ Since ...
-2
votes
1answer
25 views

How much work is required to lift an object (laying horizontally on ground) to vertical position? [closed]

Consider we know mass and length of an object. Blue line is initial position and black one is final position of an object. Confused about Work needed to lift it.
3
votes
4answers
82 views

Work done on an a pile of books

If I have a pile of books and I push the bottom one and all the pile moves with it, then, is work being done on the book on the top? If yes, is it by friction? Obviously the book is moving so it ...
1
vote
1answer
49 views

Work-Energy Theorem for Non-Constant Mass

"The net work done on an object is equal to its change in kinetic energy." Let's say that a rocket is moving upwards while expelling gas and is thus losing mass. (Non-constant mass) As the object ...
-1
votes
1answer
15 views

Conducting sphere

A conducting sphere is to be charged by bringing in positive charge a little at a time until the total charge is $Q$. The total work required for this process is alleged to be proportional to $Q$ ...
0
votes
1answer
27 views

Which direction will this object move in at the end of this process?

1) Consider an object with no net force acting on it moving with a constant velocity v. It has a momentum mv. 2) Now let a force F1 act on the object. Let the direction of this force be opposite (to ...
0
votes
4answers
104 views

Why $g$ is not negative in potential energy $= mgh$ formula

For eg. A boy of mass 55 kg runs up a staircase of 50 steps in 10s. If the height of each step is 10 cm, find his power. My question is here why are we not taking g as negative as boy is moving up ...