# Questions tagged [classical-mechanics]

Classical mechanics discusses the behaviour of macroscopic bodies under the influence of forces (without necessarily specifying the origin of these forces). If it's possible, USE MORE SPECIFIC TAGS like [newtonian-mechanics], [lagrangian-formalism], and [hamiltonian-formalism].

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### Can the curvature of a vibrating string be derived from the energy equation?

Arnold’s Mechanical Methods of Classical Mechanics page 17 says the theory of oscillation is $\dot x = -x$ and $E=x ̇^2/2+x^2/2$. The energy level sets are concentric circles in union with the ...
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### Lagrangian and Hamiltonian Mechanics: Conjugate Momentum

I am a physics undergraduate student currently taking a classical mechanics course, and I am not able to understand what conjugate/canonical momentum is (physically). It is sometimes equal to the ...
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### Boat-river problem [closed]

A river flows from east to west at 4 km/hr. From the north bank of the river, the first boat starts traveling straight towards the other bank at a speed of 10 km/h. The second boat starts moving along ...
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### Impulse imparted into a circular orbit

I am studying classical mechanics and the following problem has come up. I am not quite sure how to approach it. A particle of mass m moves under the influence of an attractive inverse square law ...
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### Understanding the use of Capstan Equation

I'm currently working on the analysis of a current capstan, I want to analyze this system using the capstan equation. The current capstan I'm working on has been built on the following parameters ...
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### Energy landscape of a spring in a potential

What does the energy landscape of a spring that is moving through an external periodic potential look like? Consider a spring that connects two particles in a periodic potential. Let us say the ...
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### How charge interact with mass? [closed]

If mass does not interact with charge, why does the mass of an electron move (means by which mechanism it moves) in an electromagnetic field? It is same like we stick ball on magnet with fevistic and ...
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### 2 objects heading towards each other at a certain distance and with initial velocity and friction coefficient [closed]

I'm not a physics student. I'm a programmer. But I found this physics problem interesting and I would like to understand how to approach it. 2 objects, A and B, heading towards each other at a certain ...
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### In statistical mechanics, why is one "allowed" to treat classical systems probabilistically?

Is the essential argument that these systems are microscopically chaotic enough that we can approximate their evolution as random (vastly simplifying calculations) and still make accurate experimental ...
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### Derivation of Hamiltonian by constraining $L(q, v, t)$ with $v = \dot{q}$

I am trying to reconstruct a derivation that I encountered a while ago somewhere on the internet, in order to build some intuition both for $H$ and $L$ in classical mechanics, and for the operation of ...
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### Does the potential energy $\alpha\ln r$ have closed trajectories for $E>0$? [closed]

Say we've got the following potential energy $$U(r)=\alpha\ln r,$$ $\alpha$ being positive constant ($\alpha\in\mathbf R^+$) . To argue whether it has closed trajectories or not we'll have to focus on ...
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### Does the acceleration formula from dynamics apply in all cases?

Can the formula for acceleration $$a=\frac{F}m$$ (where $a$=acceleration, $F$=force ,$m$=mass) be used in all cases ? Or is it an isolated formula used only for some cases ?
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### Classical Mechanics: How can i find the analytical form of the effective potential? [closed]

Question: Consider the system on the side consisting of two particles with the same mass m, connected to each other by a flexible string with fixed extension l. One of the masses is suspended and the ...
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### On the connection between the ocean of physical elements with vacuum and the formation of space - Part 1 [closed]

Abstract:- I shall put forth in this article a description of the formation of space and its gradual development into a universe while addressing the crucial case of how, why, and when. I will, ...
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### Electrical charges and energy

Since we have defined energy as the ability to do work, how come electric charges (-) and (+) be able to do work without using any energy? If lets say I have a big fixed positive charge and if lets ...
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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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### Problem while calculing the bending torque of internal air pressure in a soft actuator

this is a question I cant resolve while looking a paper I needed for my undergraduate thesis. In this image (from Modeling of Soft Fiber-Reinforced Bending Actuators, Panagiotis Polygerinos et al.), ...
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### Can a body be in both static and dynamic equilibrium simultaneously?

I was just studying statics when I realized that a body can be in both static or dynamic equilibrium at the same time but I am not so sure. My textbook says that an object at rest is in static ...
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### How to determine whether an object is a point object?

I know that we can consider an object as point object, if its size is negligible as compared to distance traveled by it in reasonable amount of time. But in my book Ncert there is questions which asks ...
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### In the equation of wave (mechanical) : $y (x,t) = a \sin(kx-wt+\phi)$;

Does the $x$ show the displacement of the particle and the $y$ shows the displacement of the wave?
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### HW: particle subject to central force with exponential logarithmic orbit

I've been working on this exercise for some time now and although I've almost got it I can't seem to make it to the end of it. Here is the exercise: A particle subject to a central force is orbiting ...
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### What happens if the impulse of a collision results in the change in velocity being greater than the speed of sound?

It is my understanding that impulse travels through materials at the speed of sound through that material (i.e. impulse through steel travels through the steel at ~5000 m/s which is the speed of sound ...
1 vote
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### Connection Helmholtz free energy and $H,M,B$ fields

Consider a magnetic system subject to a magnetic field. Here we work with the fields $H,M,B$. Now, how does a change in the Helmholz free energy depend on $H,M,B$? I have three sources that seem to ...
Why is the Hamiltonian not conserved when the Lagrangian has an explicit time dependence? What I mean is that it is very obvious to argue that if the Lagrangian has no an explicit time dependence $L=L(... 0 votes 2 answers 55 views ### Kinetic energy of a rotating body On my own, I tried deriving the rotational kinetic energy for a rotating body with an arbitrary changing axis of rotation. What I did is use the formula:$$T = \frac{1}{2}\omega^2 (\hat{n}^{T} \mathbf{... -2 votes 1 answer 39 views ### Find the acceleration of a block sliding down on an accelerating inclined place [closed] I don't understand the solution provided in the image. Using Newton's second law for forces along the x-axis (parallel to the inclined plane), shouldn't the equation be$ma = mg\sin \theta+ mb\cos \...
I have a few dots in my brain that I need to connect, one of them is: Is $\dot{\vec{r}}=\vec{v}$ true always? But $\dot{r}=v$ isn't always true? If so, in which cases both are true or not? Regarding ...