# Tagged Questions

Classical mechanics refers to the classical (i.e., non-relativistic, non-quantum) study of physics. Three major formulations of classical mechanics are newtonian mechanics, lagrangian mechanics, and hamiltonian mechanics. The latter two are rather useful in extensions to Classical Mechanics; ...

157 views

### Diffraction through the slit

In book "Quantum Mechanics and Path Integral", 3-2 Diffraction through the slit: Under the fig. 3-3, why did Feynman say that we cannot approach the problem by a single application of the free-...
230 views

### A particular case when Lagrange equation is equivalent to equation of motion on a Riemannian manifold

Suppose a particle is moving on a surface of a sphere,then it contains a holonomic constraint and so the three Cartesian co-ordinates are available with a constraint equation(equation of surface in ...
238 views

37 views

### Homework exercise: a ball hits a rigid bar [closed]

I need a hand with the following exercise: A rigid bar of mass $M$ and length $L$ is hanging vertically from it's upper side, from which it can rotate freely. A particle of mass $m$ hits the ...
64 views

### Tractrix - velocity pointing to pulling point

It is said the tractrix is the curve described by a mass being pulled by a string, where the end of the string being pulled moves with constant speed, and the mass suffers a friction force. What is ...
60 views

### Which condition is stronger - ergodicity or mixing?

Reading a statistical physics book, I've encountered the following assertion (without further explanations): [..] the presence of dynamical instability makes the trajectory of a system much more ...
37 views

### Photon transmission

I want to know exactly how light travels. Are each photon in a light beam traveling in a cosine function? I'm confused because only when it goes through polarization that it starts to show this type ...
34 views

### change of energy in changing frame of reference

Let's imagine a car that can jump onto, or off a moving train. The train moves at 10m/s. The car, on a road next to the train, accelerates to the same 10m/s, jumps off a ramp and lands on the train, ...
35 views

### Confused about shear elasticity and complementary shear stress

I am a self learner of continuum mechanic. I am confused about simple shear stress in situation similar to figure 1, in case $F_\textrm{ext}$ is caused by external perturbation by i.e., human, what ...
39 views

### Why we can use partial derivatives to tell if a force is conservative? [duplicate]

Let us, initially, analysis only a two dimension situation. Assume that $F(x,y)$ is a force dependent on the particle position (give by $x,y$) is proposed that if \frac{\partial \...
63 views

### Normal reaction [closed]

Consider a plank on a frictionless surface and a ball from a height H is dropped on this plank. There is no friction between the plank and ball. Can the plank jump up in air for any value of H? I don'...
17 views

### Slowly Varying Functions for Adiabatic Invariants - The Same as Karamata's?

In section 49 (and 50) of Landau and Lifschitz's "Classical Mechanics", adiabatic invariants are discussed, which are related to functions which vary adiabatically or "slowly" with time. Admittedly ...
49 views

### What are the assumptions behind the Lagrangian derivation of energy?

What are the assumptions behind the Lagrangian derivation of energy? I understand that we're searching for a function $L$ that describes a set of physics so that solving the energy minimization ...
91 views

### A Canonical Transformation that deletes one canonical coordinate?

I am self studying some classical mechanics, and came across a problem in Goldstein that has me stumped. It is problem 1 in chapter 10. It basically says "Given some conservative system show that a ...
36 views

### Why does the kinetic energy of a particle moving in circular motion increase when the turn radius decreases and no torque is acting?

Why does the kinetic energy of a particle moving in circular motion increase when the turn radius decreases and there is no torque acting? E.g. if a planet is rotating about its axis and it shrinks to ...
52 views

### Magnetic field of rotating capacitor [duplicate]

Does the rotating charged capacitor (both plates) produce magnetic field? and what about rotating both plates in opposite directions?
36 views

### Euler-Lagrange problem of single mass double pendulum in plane [closed]

Problem: "A rod with a length of $l$, mass $m$, is attached by a thread of length $l/2$ according to figure. The rod may perform small, planar swings. Determine its eigen-frequencies." Figure: ...
57 views

38 views

### Are physical functions always differentiable [duplicate]

I know that physicist usually don't really think too much about differentiabillity of functions. Usually there are at most finite many points where functions aren't differentiable and if there are ...
36 views

### When will a moving vehicle stop faster: when the brakes are applied and the wheels are slipping, or just before? [closed]

When will a moving vehicle stop faster: when the brakes are applied and the wheels are slipping, or just before the wheels start slipping? Explain why.