Questions tagged [work]

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

Filter by
Sorted by
Tagged with
2
votes
1answer
54 views

This clever device moves heavy rocks upwards against gravity using buoyancy. Where is 'the work' coming from to move the rocks upwards?

So I saw this machine whilst researching the pyramids, and I've become completely fascinated by it. It seems to beautifully demonstrate many of the conundrums of work done, but remains alluring enough ...
1
vote
1answer
68 views

Why work done to submerge a ball is $pV$?

In this stack post Mr.mark says the work done to submerge a ball is $pV$. I don't seem to comprehend this . I believe this would be answered in a comment but and answer could help me show my ...
0
votes
1answer
26 views

The equation of raising the temperature of the water using the electric heater

I've been confused of the following equation The electric heater exists which can generate $P[cal/s]$. $t:=$time which is required to raise the temperature of the water of $m[kg]$ from $a[°C]$ to $b[°...
3
votes
4answers
113 views

Work done in submerging a weightless sphere, I am getting exactly half the correct, can someone point out my mistake! [closed]

This is the question: A sphere of radius 0.4 m and having negligible weight is floating in a large freshwater lake. How much work is required to completely submerge the sphere? The density of the ...
1
vote
2answers
54 views

Why static friction does work on rolling bodies? [duplicate]

I'm studying the rolling motion, but, Why the torque by static friction does work? If the point of application is at rest relative to the inclined plane, therefore, the point of application doesn't ...
0
votes
3answers
56 views

Total work done on a satellite

I have a question about the concept of work in relation to conservative and non-conservative forces. Is Total work done $=$ change in kinetic energy or change in total energy $?$ This question arose ...
0
votes
2answers
41 views

Unsteady flow equation

I am having trouble understanding how the unsteady flow equation is formulated. Why does it say that the RHS of the equation(change of energy in system) is made up of internal energy, kinetic energy ...
-1
votes
0answers
20 views

Work done moving a negative charge vertically

This is the explanation according to the book: There will be work done in moving the negative charge from its initial position to y = 0. However, in moving the negative charge from y = 0 to the final ...
1
vote
1answer
41 views

Work done moving a satellite into higher orbit

I am confused about the concept of work in relation to conservative and non-conservative forces. When transferring a satellite from a lower orbit into a higher orbit via a Hohmann transfer, my ...
0
votes
1answer
67 views

Mechanics: why is the work done by the weight of the object not taken into account in this question? [closed]

A object of mass $0.3 \,kg$ is released from rest above a tank containing water. the object takes $0.8$ seconds to reach the water surface. there is no instantaneous change of speed when the particle ...
0
votes
1answer
29 views

Gasoline has a very high molar heat capacity. Is this a good thing for its use in engines?

Wikipedia states that the molar heat capacity of gasoline is $228 \, J/mol\cdot K$ (https://en.wikipedia.org/wiki/Table_of_specific_heat_capacities). This is more than twice that of liquid water ($75....
1
vote
1answer
58 views

Mechanics: what does work done against resistance really mean?

Does ''work done against resistance'' mean the force needed to overcome friction i.e. the magnitude of the frictional force itself x distance? or does it mean the work done by the net force i.e. (the ...
0
votes
1answer
35 views

Mechanics: question about forces

Can we find the work done by the weight of an object? If not, why? When finding the net work done we consider all the forces applied on the particle. But is the weight not a force that needs to be ...
0
votes
2answers
48 views

Can a constant pressure expansion occur reversibly?

I'm currently reading section 19-7 in McQuarrie's physical chemistry textbook, but I'm getting a bit hung up on the possibility of reversible processes at constant pressure, since up to this point the ...
4
votes
4answers
351 views

How can a rigid body's weight do work on it to make it rotate?

Consider a cylinder that rolls without sliding on an inclined plane. If it's placed at the top of the plane, with its center of mass at a height $h$ from the bottom, it will have a potential energy $...
1
vote
3answers
86 views

When is $\Delta U=nC_{v}\Delta T$ true?

Given that $1$ g of water in liquid phase has volume $1$ cm$^3$ and in vapour phase $1671$ cm$^3$ at atmospheric pressure and the heat of vaporisation of water $2256$ $\frac{J}{g}$; the change in the ...
0
votes
1answer
49 views

Closed system in thermodynamics

If a closed system experiences a new work transfer while it undergoes a reversible process, does a net heat transfer from the system always occur? If not, please provide an example when a net heat ...
1
vote
2answers
68 views

How does the work-energy theorem relate to the first law of thermodynamics?

The work energy theorem states that the net work on a particle is equal to the change in the kinetic energy of the particle: $$W_{net}=\Delta K $$ My first question is whether this formula (the work-...
1
vote
0answers
35 views

Why is work done equal to force×displacement? [duplicate]

I have understood that work done depends on force and displacement but I have not understood that why does the product of these two gives work done and not multiplied by some constants or raised to ...
-3
votes
1answer
57 views

Is energy, as we know it, “persistent”? [duplicate]

Suppose I raise a ball (with my hand) to some height. I am doing some work against gravity and storing potential energy in the ball. However, once I loosen my grip, or just sweep my hand away from ...
1
vote
1answer
56 views

Work with thermodynamical equilibrium condition

A thermodynamic system being in thermodynamic equilibrium is characterized by the property that for every thermodynamic potential $F$ which describes the system, its differential $dF$ is zero. Let ...
1
vote
3answers
97 views

How can two equal forces applied on the same mass $m$ cause the same displacement in different amounts of time? [closed]

in my textbook the concept of power is explained through this example: a man lifts a bucket containing cement to a certain height; a freight elevator can lift the same bucket in less time. It then ...
0
votes
0answers
54 views

How to find work done when external force is doing work?

A heat conducting piston can freely move inside a closed thermally insulated cylinder of volume $2v_0$ filled with an ideal gas. In equilibrium, the piston divides the cylinder into two equal parts ...
1
vote
2answers
55 views

Why is the minimum work done not negative in this case?

I was going through my grade 10 physics textbook and noticed that $F S \cos 180^\circ$ (work done will be negative) is less than $F S \cos 90^\circ$ (work done is zero) but it is still stated that $F ...
1
vote
2answers
35 views

Work energy homework question

Equal force $(F>mg)$ is applied to the string in all three cases. Starting from rest point of application of force moves a distance of 2 metres down in all cases. In which case the block has ...
0
votes
0answers
32 views

Why do the horses mechanical efficiency seems low relatively to that of human cyclists? [closed]

According to this article a horsepower is equal to the average power production of a horse over an extended period of time. An elite cyclist can produce about half of horsepower over an extended ...
4
votes
1answer
59 views

Does diffusion do work?

Imagine I drop a sugar cube of 2 cubic centimeter into a cup of distilled water and then wait for the sugar molecule to break apart and dissolves into the soon to be solution. Is there any work done ...
0
votes
1answer
27 views

Mass, Time, Distance, a lunkhead Digital designer, and a question I really should know the answer to

I'm an engineer, but I'm an electronics designer, and mechanical math makes my head hurt. So, yes, I should be able to figure this out using my college textbooks, but I was never that good of a ...
0
votes
3answers
31 views

Why the weight vector is perpendicular to the displacement of the object being moved by the tension force in the conical pendulum?

Can someone explain why, in the conical pendulum, the weight vector is perpendicular to the displacement of the object being moved by the tension force in the system? I understand that the tension ...
12
votes
5answers
878 views

Why the work done in a conservative field around a closed circle does not vanish when calculated in cylindrical coordinates?

I was solving problem 2.4.13 from the book "George B Arfken, Hans J Weber - Mathematical Methods For Physicists- Sixth edition" and the problems was that: Problem 2.4.13 A force is ...
0
votes
1answer
28 views

Electrostatic stored energy of a continuous charge distribution

If I have a charge distribution A at infinity and and another charge distribution at origin, say B, then the energy stored in the system when I bring the charge distribution A from infinity to a ...
3
votes
3answers
218 views

Rule of the Work done by a force

I have been always taught that Work done = force x distance through which the force was applied. but recently in the elasticity I have been taught that W= (1/2) (F X D). why did we multiply it by a ...
0
votes
0answers
25 views

Electrical work sign convention

If I understood the correct sign convention it's as shown in the below sketch:
0
votes
2answers
53 views

Conservative Force in a loop

Could someone prove mathematically that why in this situation a charge could move in a loop with net work done. Could someone explain this paragraph to me.
2
votes
4answers
83 views

Where does $W_{net} = \Delta K_e + \Delta P_e$ come from?

I was learning how to derive Bernoulli's equation and saw that he was using the work-energy theorem as $$W_{net} = \Delta K_e + \Delta P_e.$$ What I know is that Work-energy theorem says that, $W_{...
0
votes
0answers
21 views

What is the difference between irreversible and reversible isochoric processes done on an ideal monatomic gas in a frictionless system?

Suppose we had two thermal reservoirs at $T_{c}$ and $T_{h}$ with $T_{c} < T_{h}$ and an infinite series of thermal reservoirs with a continuous range of temperatures between $T_{c}$ and $T_{h}$. ...
1
vote
1answer
37 views

Does relative work done affect temperature of a body? [duplicate]

Imagine a bus travelling at a speed of 20m/s towards the positive x-axis with respect to ground frame. That bus is quite long(just for a safer Side) and two persons 'A'and 'B' located inside that bus ...
0
votes
3answers
52 views

Work done on a charged particle

Suppose we have a stationary configuration of source charges and we want to move a test charge $q$ from point $a$ to point $b$. How much work will we have to do? Since the force on $q$ is $\vec{F}=q\...
1
vote
2answers
64 views

Total energy vs the kinetic energy of a body

Now, we know, $$∆T = \int_a^b\vec F_\text{ext}\cdot d\vec s = W$$ Where $∆T$ is the change in kinetic energy of the object and $W$ is the work done on the object by $F_\text{ext}$. In some books, they ...
3
votes
2answers
40 views

Would it be easier to break a stack of planks joined together or when they have gaps between them?

If there is a stack of n identical planks (say n=5) and we need to break them (like in karate), would it be easier (i.e. would it require less force) if they are stacked together (figure on the left) ...
0
votes
4answers
60 views

Is work a transfer of energy in general, or is it a transfer of kinetic energy?

the net-work is the change in kinetic energy, so is every one of the "works" done on an object solely transferring energy through kinetic energy? In other words, if I was to lift an object ...
0
votes
3answers
70 views

Why there's no work in adiabatic free expansion? [closed]

We say that because there is no external force on the system, the work done on the adiabatic free expansion is $0$(If this is wrong, correct me please). But there is a pressure and volume change in ...
-3
votes
2answers
47 views

What is the impact of work done on motion? [closed]

An object of mass $10Kg$ is travelling at a constant acceleration of $10m/s^2$. A resistive force has $-50 J$(negative fifty joules) of work done on the object. What is the impact of that negative ...
0
votes
2answers
32 views

Work done in Free Expansion of an Ideal gas

We define the work done in gaseous expansion as (External Force)*(Displacement of the piston) The work done in free expansion, therefore, comes out to be 0 as the external pressure is 0. But if we let ...
1
vote
2answers
71 views

Infinitesimal Changes - Notations

in my thermodynamics class we saw the following formulas: $$ dS = \frac{\delta Q}{T} $$ and $$ \delta W = PdV $$ This was part of a review of thermodynamics that we have seen previously; however, in ...
0
votes
2answers
95 views

Does the concept of work make kinetic energy Galilean invariant?

I have read at this site that the work is defined in such a way that kinetic energy will be Galilean invariant. Could someone explain a little more about what is meant by this?
1
vote
1answer
33 views

Understanding of Kinetic, Potential and Change in Energy

From what I understand, energy is defined as the ability to do work. What does this actually mean and how is it different from work itself? Also, according to my teacher, absolute energy does not ...
1
vote
2answers
79 views

How is the definition of work motivated?

For most dynamical variables in classical physics, I can understand how one may have decided to introduce them as a result of some "incompleteness" in Newton's laws of motion. For example: ...
1
vote
1answer
52 views

Net Force vs Net Work

I hope you are doing well :) When I was practicing, I came upon this question: On a horizontal frictionless surface there is a Spring with a Spring constant is 50 N/m. Initially, the spring is at its ...
0
votes
4answers
157 views

What comes first: Work or kinetic energy?

Suppose we have a body initially at rest. Now a force ($F$) is continuously applied on it and it gets displaced by some distance $x$. My tutor said that from work energy theorem it gains kinetic ...

1
2 3 4 5
44