wrobel's latest activity

Nice way to prove the law of sines but what about to get ##2R## in the same spirit? :)

Most funny thing is that the system is Hamiltonian (see #18). Even the "energy" integral exists: $$\frac{1}{2}\dot...

I deeply respect people who are engaged in self-education. Nevertheless the problem of self-education is as follows. A person reads...

I have always been wondering how such a banal thing can generate endless discussions.

NTesla: Consider the vertical part of the chain. Let ##N(x)## be a tension force that acts in the section that lies at the height ##x##...

look carefully :) My answer is the same as one in the original post

my version is $$\ddot x=-\frac{gh}{x+h},$$ where ##x## is a length of the horizontal tail

then it must be incompressible as well. Is the chain under consideration incompressible? Why? If it is incompressible it stops when...

In exercises as a rule pulleys are considered with massless strings. This is a hypothesis it does not follow from equations of motion...

why?

In principle one can introduce a tension force along the chain and write down the 2nd Newton law for each ##\Delta m##. But where...

A motion of a rigid body with a fixed point ##O## is described by the following equations $$m\boldsymbol{\dot v}_S=\boldsymbol F,\quad...

Each solution is bounded for ##t\ge 0##. This follows from the estimate $$\frac{m}{2}\frac{d}{dt}|\boldsymbol v|^2=m(\boldsymbol...

Here is a sketch of deduction of the Lagrange equations by means of the covariance argument. I believe that it is a suitable substitute...

Strictly speaking the first Newton law says that inertial frames do exist. By definition an inertial frame is the frame in which...