All Questions
Tagged with classical-mechanics work
214
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Drawbacks of Quasi-Static process for lifting a block
Definition of Quasi-static: A quasi-static process is a thermodynamic or mechanical process that occurs very slowly, allowing the system to remain in a state of equilibrium at all times.
While ...
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Is impulse functionally equivalent to work and therefore expressible in Joules?
I am trying to understand things at at a fundamental and conceptual level.
Givens...
1 kg mass
Mass is at rest (relatively, of course)
Mass is on an idealized frictionless surface
1 N of force is ...
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Work Done by kinetic friction in Circular Motion
We know when an object is moving in a circular motion on a rough horizontal surface, direction of kinetic friction is constantly. Thus, fto calculate the work doen by friction, we need to use ...
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Areas with anti-parallel gravity in classical physics
I cannot indicate an error in the following reasoning if it is done in the framework of classical physics.
Let's make the imaginary setup with two wedges and the ball, when the gravity in the left ...
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Work performed by hydrostatic pressure
One should be able to show mathematically that the hydrostatic work done by an environment on an object undergoing a volume change $\Delta v$ should be $p \Delta v$, where $p$ is the (constant) ...
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3
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The conservative force [closed]
I read about the definition of the curl.
It's the measure of the rotation of the vector field around a specific point
I understand this, but I would like to know what does the "curl of the ...
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Vanishing virtual work done by non-holonomic constraints
I was reading classical mechanics by NC Rana. I was reading a topic on vanishing virtual work done due to constraint forces. How do you prove that the virtual work done by non-holonomic constraint ...
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Is it possible that work is being done on an object, it's kinetic energy doesn't changes and still the body is transferred from one point to another?
Recently, I read a book about Electrostatics which stated that "Electrostatic Potential at a point is defined as the work done to move a unit charge from a reference point (generally taken as ...
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Why is force "accumulated" more at a higher speed?
I tried to understand why kinetic energy is proportional to the square of velocity. In this endeavor I stumbled upon a book "Emilie du Chatelet: Daring Genius of the Enlightenment" (ISBN 978-...
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The role of the virtual work principle
Lanczos' masterpiece "The Variational Principle of Mechanics" has, on page 76, the following statement:
Postulate A (virtual work): The virtual work of the forces of reaction is always zero for any ...
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Does every object have an infinite amount of energy? [duplicate]
If energy is defined as the capacity to do work, and the formula for work is force times displacement, if we place an object on a frictionless surface and apply any amount of force to said object, the ...
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Can a conservative force not conserve mechanical energy because of explicit time dependence?
Let us define a conservative force as being a force whose work is path independent. Then, in particular, a vanishing force is conservative.
If a force acting on a particle can be written from a scalar ...
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Why is the gravitational potential energy lost not subtracted from the required work done in the given problem? [closed]
An elastic string of natural length $l \;\text{m}$ is suspended from a fixed point $O$. When a mass of $M \;\text{kg}$ is attached to the other end of the string, its extension is $\frac {l}{10} \;\...
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Where does the power delivered to car's wheels go?
Okay, so power is work/time. Most cases, when power is provided to something, energy is gained as kinetic energy or lost to friction.
But in a car, the engine puts power ( torque x rpm/5252) to ...
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Work using angle vs. displacement [closed]
I am trying to calculate the work done on this wheel as it undergoes one full revolution, and is rolling without slipping.
I am aware that work can be calculated either using the integral of force ...
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Should the work done on a rigid body be calculated with respect to the point of application, or the center of mass?
I'm trying to understand work calculation for a force acting on a rigid body (as opposed to a point particle).
My understanding is that the same basic principle applies: the work done by force F on ...
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Why does a system have to be holonomic?
So I'm doing some work from Taylor's mechanics book. He says for the problems in the book, we require the system to be holonomic - that is the number of generalized coordinates = number of Deg. of ...
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How can the Joule be the unit of both work and energy?
Say a person applies 1 N to a box with a mass of 1 kg, displacing 1 m. This is one Joule of work
(1 N for 1 m).
Now say the person applies 1 N to a box with double the mass, displacing 1 m as well. ...
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Work Done on a rotating thin rod by hinge Forces
So I was studying the concept of rotational energy through a video, and the guy presented a problem,
It's like this:
"Suppose a thin rod of mass M and length L/2 is hinged from one end. Then, it ...
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Why is the work done by moving an object up vertically not greater than mgh
Watching Walter Lewin's classical mechanics. In lecture 11 he says when moving object up vertically distance h, the work done by gravity is -mgh, which makes sense. But then he said the work done by ...
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Where does $W = \Delta E$ come from?
My textbook states the following:
$$W_{net}=W_{non−conservative}+W_{conservative}$$
$$W_{non−conservative}=ΔKE+ΔPE$$
$$W_{conservative}=−ΔPE$$
$$W_{net}=ΔKE$$
$$W=FDcos(Θ)$$
However, my teacher states ...
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Why isn't work $Fd \sec \theta$? [closed]
In the following image if force the triangle PAN was right angle at P then the component of force in the direction of displacement would be $F\sec\theta$ so work $F*Displacement(AC)*\sec \theta $.
I ...
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Work of friction along a circular path using dot product
Good day guys, I was working on circular motion and was wondering about the following:
I have seen that the work done by friction along a circular path is given by
$$W = F_fS$$
I was wondering if it ...
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Conservative forces and Variation
I am currently studying "Classical mechanics by Goldstein" and have just started. The book introduced something simple. For a conservative force, the work done in taking a mass from one ...
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Getting different answers by different methods for angle made by a pendulum moving with constant acceleration
A point mass $m$ is hanging by a string of length $l$ in a car moving with a constant acceleration $a$. Using car frame and pseudo force, we easily get that the angle made by string with vertical is :
...
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Does work depend on a point of reference? [duplicate]
Imagine there is me, Earth and some other guy. Me and a guy move parallel to each other at the speed of 1000m/s relative to Earth.
I am so fit that my mass is 0.5kg, so when a force of 1N in the ...
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Conditions for a force to be conservative - Does the second condition imply the first? [duplicate]
John Taylor's Classical Mechanics says this...
I was wondering if the second condition already implies the first? I mean, are there situations where the first condition is violated even though the ...
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Can a force in an explicitly time dependent classical system be conservative?
If I consider equations of motion derived from the principle of least action for an explicitly time dependent Lagrangian
$$\delta S[L[q(\text{t}),q'(\text{t}),{\bf t}]]=0,$$
under what circumstances (...
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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-...
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Is there a non-counterfactual definition of energy? [duplicate]
I have once heard that the definition of energy is "the ability to do work". However, that is a counterfactual definition, because a physical system can have that ability without actually ...
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Does potential energy actually exist? Or is it just a useful mathematical model? [closed]
The title basically covers it. I've actually thought about this question for a while now, and I am still not sure if I have a definitive answer. Most potential energies seem to just be the work that ...
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Work done by tension on a system-generalisation
In All the Classical Mechanics problems I have come across so far, There's one thing that happens invariably: That the work done by tension is zero. Mostly, It simply happens because the (massless) ...
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How do we justify that work is a "transfer of energy" in the general case?
By the work-energy theorem, we can justify that the work on a particle due to the net force equals the change in kinetic energy of the particle. In compact notation,
\begin{align}\tag{1}
W_{\text{net}}...
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Is work done relative according to the theory of special relativity?
I performed a thought experiment.
Consider a body $A$ and another body $B$.
Body $B$ is moving at velocity $v$ in direction $x$ with respect to $A$. This implies that body $A$ is moving at velocity $v$...
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Why do manual treadmills burn more calories than automatic treadmills?
Studies show that manual treadmills burn 30% more calories than automatic ones.
Let's assume that there is no air friction.
The figure is a diagram of the forces acting on a person running on the ...
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What is the difference between the principle of virtual work and the principle of virtual displacement?
When I read Reddy's book, "Energy Principles and Variational Methods in Applied Mechanics", Chapter 5.1. I am confused with the two jargons "the principle of virtual displacement" and "the principle ...
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Consolidating two ways to calculate work
I was wondering if I could get some help closing some fundamental gaps in my intuition of work, as it relates to force and distance travelled.
Scenario
Say we pull a 1kg box along the ground. We pull ...
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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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Kinetic and Potential Energy of a multi degree of freedom (MDOF) system
Consider the following MDOF system:
$M\ddot x+Kx=F$
where $M$ and $K$ are the mass and stiffness matrix respectively, and $x$ and $F$ are the displacement and force vectors.
How can one determine the ...
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Sign of work done by friction
In Goldstein's classical mechanics (3rd ed.) we read:
"The independence of W12 on
the particular path implies that the work done around such a closed circuit is zero,i.e.
$$\oint \textbf{F}.d\...
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How can potential energy increase? [closed]
If work is done on a body, the energy of the body increases. If work is done by the body, energy decreases. When we take a body up to some height, some work is done by us on the body, which is stored ...
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Does work-energy theorem account for thermal energy?
Suppose a box (which I assume to be a rigid body) with an initial velocity that starts to slide on a level surface with friction. Imagine this experiment is done in vacuum, so there is no air drag or ...
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Power when work is 0
Imagine a rocket of mass m that is at a constant altitude. Gas velocity v. It is necessary to find the power P of the engine. I have a problem: to find the power, you need to divide the work by the ...
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Work done on a body and work done by the body
I want to know that, if we suppose that, if a ball is falling freely then work would be done on the ball by gravity so energy would be given to the ball? and when the ball rebounds after striking the ...
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Aren't the virtual work/virtual power principles in mechanics simply solving for the vector differential equation of motion in a preferred direction?
My conceptual understanding of the virtual work/virtual power principles is that, by hypothesizing "virtual displacements"/"virtual velocities", one can solve the equations of ...
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Do rigid bodies experience work greater than or equal to that of point particles?
Consider the following two scenarios in outer space:
A yo-yo whose string is pulled by a constant force.
The same yo-yo as before although this time, the string is fully unwound and attached to the ...
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Law of Conservation of Energy ambiguity in Giancoli textbook
In my version of the textbook by Giancoli: Physics for Scientists and Engineers, in chapter 8, there is a formulation of the law of conservation of energy that seems unintuitive and correctable to me. ...
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Work in thermodynamics and work in mechanics
work in mechanics
$w=\vec{f} \cdot \vec{s}$
work in thermodynamics
$w=-p \Delta v$
I don't understand why $ \vec{f} \cdot \vec{s}= -p \Delta v$ ?
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What work does a microwave oven do? [duplicate]
I learned that when energy is transfered it either produces work or it becomes thermal energy (heat).
Work implies a force that acts on an object producing changes in its position.
I'm learning these ...
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What is the status of the Work-Energy Theorem? [closed]
All the 'proofs' of the Work–Energy Theorem that I have seen show that the work done by the resultant force acting on a body is equal to $\Delta \left(\tfrac 12 m v^2)\right)$ for that body. [It's ...
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