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

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2answers
71 views

How come weight doesn't affect the rebound height on a net?

According to my text book two unequal masses, (80kg and 50kg) fall on a net and the work done by that net is calculated by $\frac{1}{2}kx^2$. This work is then transformed into kinetic energy for both ...
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1answer
173 views

How to calculate work when a block is moving with constant velocity?

How to calculate work when a block is moving with constant velocity? As we know $f=ma$, and for constant velocity $a=0$, so $f=0$ and $w=fs=0$? Can anybody make it clear?
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1answer
196 views

Is it true that a Space Shuttle launch is powerful like an “average” nuclear explosion?

Kind of an odd question here. First let's define what an "average" nuclear explosion is, because that's quite a controversial term - "average". Considering that the peak of nuclear tests was at the ...
1
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1answer
187 views

Work done by an expanding gas

Today in an engineering thermodynamics lecture, the professor gave an example of a gas doing work. We had a cylinder full of helium at a pressure of something like 200 kPa absolute and the valve was ...
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4answers
144 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 ...
2
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2answers
194 views

Question related to work done and energy

Suppose you lift a box from the ground over your head. You will be using energy as there is work done. But when you keep the box lifted over your head, aren't you using any extra energy?
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4answers
995 views

Is potential energy and “work done” the same thing?

Is potential energy and "work done" the same thing? If they are not one and the same thing then why is potential energy always associated with "work done"? Could you explain me with some examples?
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4answers
246 views

Work is force multiplied by distance What is this distance? [closed]

What is the distance which the force is multiplied by it to get the work done? a) The distance of the body motion while the force was touching it? b) The total distance of the body motion?
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0answers
41 views

How does pressurized gas constantly push?

If a gas, such as hydrogen, is pressurized into an air tight container, a force in terms of pascals (or whatever unit you want to use) is exerted, correct? That is what pushes against every surface ...
1
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1answer
788 views

What is happening to rotational kinetic energy when moment of inertia is changed?

I know this question is asked here a lot, but I just had to ask this to finalise the concept. When a system lets say a rod of length $L$ and mass $M$ is rotating with angular speed $omega_1$ its ...
2
votes
2answers
551 views

Work done by Lorentz Force in case of motional emf

In the classical example of the slidewire generator where the rod slides on a U-shaped conductor in a magnetic field, we get a charge separation due to the Lorentz force. The way the induced emf is ...
4
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2answers
589 views

Is any work done if I walk in a circle?

My friend and I were arguing about this and I was wondering if someone out there could settle this for us. Basically, he and I were walking to buy some stamps. When we were on our return trip he ...
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2answers
68 views

Finding the value of velocity $u$ [closed]

A block of mass $m$ is pushed towards a moveable wedge of mass $\eta m$ and height $h$, with a velocity $u$. All surfaces are smooth. The minimum value of $u$ for which the block will reach the top of ...
1
vote
1answer
80 views

Exertion from swinging on a playground swing

I've read about how by tilting one's body one changes one's center of mass while swinging on a playground swing, and thereby increases the energy of the swing. But I would like to get a better sense ...
1
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2answers
182 views

Does gravity exert more “power” when an object is traveling faster?

So, this question arose when I was pondering the meaning of horsepower and torque in cars. I thought of the following question: There is a 1 kilogram weight on planet M. Planet M has no atmosphere ...
0
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2answers
159 views

Why does the coefficient of performance need to be calculated with $W + Q$?

How much work must a heat pump with a COP of 2.50 do in order to extract 1.00 MJ of thermal energy from the outdoors (the cold reservoir)? The first formula that came into my mind after reading ...
2
votes
1answer
393 views

What is the difference between $Q=\Delta U+W$ and $\Delta U=Q+W$?

Is $Q=\Delta U+W$ for when the the work is done from the system while $\Delta U=Q+W$ is for when the work is done by the system? Will anybody explain this to me, please? When do we use $Q=\Delta ...
1
vote
2answers
244 views

Increase in velocity by loss of mass? [closed]

A trolley of mass 300kg carrying a sand bag of 25kg is moving uniformly with speed of 27km/h on a frictionless track. After a while, sand starts leaking out of a hole on the floor of the trolley at ...
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1answer
1k views

Work in circular motions

Suppose that a satellite circles around a planet that exerts $2000N$ of gravitational force on the satellite. I understand the fact that since the circular motion and the centripetal force are ...
0
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2answers
298 views

How do voltage and voltage drops over a circuit relate to work done?

I have a few remaining uncertainties when it comes to voltage. I numbered the paragraphs in my thought sequence for easier reference. In a series circuit, I know voltage is the electric potential, ...
6
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2answers
302 views

What's the difference between work in thermodynamics and mechanics?

What is the difference between work in thermodynamics and work in mechanics?
0
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0answers
227 views

Work done by rolling vs skidding friction force

Two identical bicycles having equal weight riders are traveling along a level road adjacent to each other with the same non-zero velocity. Bike A, (the "skidder"), applies the rear brake strongly ...
8
votes
2answers
246 views

What is the mechanism by which magnetic fields do work?

I've seen some conflicted answers to this question in texts and on the web, in the case of a dipole, for example. Do magnetic fields do work directly, or is it their induced electric fields that do ...
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1answer
70 views

What constitutes work?

I'm asked: "An object is moving along a floor at constant velocity. Thinking about this situation as realistically as possible, is work being done on the object?" And the solution is: "Work is ...
3
votes
3answers
1k views

Why doesn't static friction decelerate a rolling body?

I know that static friction isn't the cause of deceleration of a rolling body. But if static friction is the only force in the horizontal direction, then shouldn't there be some acceleration produced ...
0
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0answers
70 views

How to relate compression ratio to work input for a compressor in a heat pump

So I need to calculate the COP (Coefficient of Performance) for a 6-ton air conditioner system in terms of the compression ratio. I understand that: $$COP=\frac{Q_L}{W_{net,in}}$$ I cannot find out ...
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2answers
311 views

Work done by a conservative force

Wikipedia: A conservative force is a force with the property that the work done in moving a particle between two points is independent of the taken path. Equivalently, if a particle travels in a ...
0
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1answer
298 views

Calories burned doing 1 squat [closed]

To calculate the calories burned doing 1 squat, wouldn't it simply involve the distance that your center of mass is moving and your weight? I read some other article that said your legs act as levers, ...
0
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1answer
268 views

Work done on gas by piston [closed]

In this problem there is a cylinder that is closed at both ends and has thermally insulated walls. It is divided into 2 parts by a movable, frictionless, thermally insulated piston. There is a ...
2
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2answers
320 views

Why can't the units of work and torque be interchanged? [duplicate]

When I'm studying about work and torque, I found that their unit are the same. But, why don't we use Joule (unit of work) instead of Newton-meter (unit of torque)? Since $\mathrm{1\ Joule = 1\ Nm}$, ...
4
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2answers
135 views

Work done on stationary rocket

Suppose I have a rocket thats exerts a force (with negligible loses in mass), which cancels out the downward force of gravity. Clearly my rocket could be moving at a constant velocity (ignore air ...
0
votes
2answers
966 views

If I lift a box vertically, why is the work I do equal to the distance I lift it times the force of gravity on the box? [duplicate]

I have problems fully understanding the concept of work, so please forgive me if this is simple. If I take a box of mass $ m $, and lift it a distance $ d $ vertically, why is the work I have done ...
1
vote
0answers
417 views

Work, Energy, Power, Force question [closed]

Question: 3 boys push a small car 25 m up a hill inclined at 19° to the horizontal. The car has a weight of 860 N and they push it at a steady speed of 0.5 m s-1 against an opposing force of friction ...
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2answers
107 views

almost same mass, same distance, different energy needs

Imagine a car, driving 10 km at constant speed in 6th gear. There will be a measurable fuel consumption. Now imagine the same car driving 10 km again at a constant speed (same as above) in the 1st ...
0
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1answer
1k views

Does a force do work on an object with constant velocity?

I know that a force does no work on an object if the object's displacement is zero, but if an object is moving at a constant velocity $\bar{v}$, and a force $\bar f$ (let's say that $\bar f$ and $\bar ...
0
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1answer
266 views

Work done should be positive but coming out negative?

$\int\frac{GMm}{x^2}dx$ where $x$ varies from $\infty$ to $r$. Situation we are bringing a very small mass from infinity to a distance r in the gravitational field of Earth with constant ...
2
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6answers
1k 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 ...
1
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3answers
7k views

Why work is a scalar and not a vector?

Work (in physics) is a scalar but why? and why not a vector?
2
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2answers
289 views

Signs in proof of gravitation potential energy (GPE)

Proof of gravitational potential energy. Work done by gravity in bringing mass from infinity to a distance of $r$ between masses. When we use the integration formula and arrive at the answer we ...
0
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1answer
569 views

Solve a problem of work and energy

A man pulling sled of his daughter by a massless rope, climbing a snowy hill whose slope is equal to 15 °. Considering that the mass of the sled is $4Kg$, the girl's $26Kg$ and $\mu _c = 0,25$, ...
0
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2answers
654 views

Why does the amount of energy transferred depend on distance rather than time?

The change in energy of an object can be determined by the work equation, where work is the change in energy: $$ W = F \cdot d $$ I conceptualize the transfer of energy as simply a series of small ...
2
votes
2answers
262 views

Does a different opposing force affect work?

Suppose a man exerts $10~N$ as he lifts a $1~kg$ box a distance of $2~m$ against Earth's gravity. To determine work we can use the following equation: $$ W = F \cdot d \\ W = (10~N) \cdot (2~m) = ...
2
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1answer
53 views

Work Done On a Body When It is Not in Contact with the agent of the Force

Is it necessary for work to be done on a body that the agent of the force remains in contact with the body? For example, if I hit a football with my foot with a small amount of force and it moves a ...
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2answers
812 views

Non-conservative field?

A conservative field is a function of position/configuration, what about a non-conservative field? It's a function dependent on what?
1
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1answer
369 views

Why the electric force does no work on the charge when perpendicular to the field?

I was reading my physics textbook and came across this sentence: When a charge moves in an electric field, unless its displacement is always perpendicular to the field, the electric force does ...
3
votes
1answer
85 views

Work done by vibrating string

figure from http://webusers.physics.illinois.edu/~m-stone5/mma/notes/amaster.pdf The string has fixed ends, a mass per unit length of $\rho$, and is under tension $T$. This source claims that "the ...
5
votes
7answers
2k views

If the net work on a particle is zero, can the speed change?

The following question was on a quiz in physics class: If the net work done on a particle is zero, which of the following statements must be true? a) The velocity is zero b) The velocity is ...
8
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3answers
668 views

Bird flying in a cage

Assume that you are holding a cage containing a bird. Do you have to make less effort if the bird flies from its position in the cage and manages to stay in the middle without touching the walls of ...
1
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2answers
2k views

Proof of conservation of energy?

How is it proved to be always true? It's a fundamental principle in Physics, that is based on all of our currents observations of multiple systems in the universe, is it always true to all systems? ...
3
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1answer
83 views

The lab have a constant electric field and a constant magnetic field, what is the electric and magnetic field inside a conductor and far from it

The following is an old question from an exam in a Physics $2$ course I am taking, I have tried to solve the question and after I thought I got the answer I looked at the solution and saw it isn't ...