wrobel's latest activity
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wrobel replied to the thread Undergrad Axial angular momentum calculation.It is a covector in the Lagrangian formalism but not in this context. Yes ##\frac{\partial L}{\partial \dot x}## is a covector on the... -
wrobel replied to the thread Undergrad Axial angular momentum calculation.That's wrong. Angular momentum is a vector. It is a pseudovector to be precise. Just by definition: ##\sum_k m_k\boldsymbol... -
wrobel replied to the thread Undergrad Properties of angular momentum.I can just explain what one actually should understand regarding this stuff. Assume we have a system of particles ##A_1,\ldots, A_N##... -
wrobel reacted to Ibix's post in the thread Graduate Is 'Velocity of Transport' a Recognized Term in English Mechanics Literature? with
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So it's basically the "extra" velocity something like a car's wing mirror has if you subtract the car's COM's velocity? I don't know any... -
wrobel replied to the thread Undergrad Is energy really conserved?.In face-to-face communication I would first ask to write down the formula of kinetic energy of a rigid body and then to provide... -
wrobel replied to the thread Graduate Help in understanding this derivation of Lagrange Equations in Non-Holonomic case.There is a nice theorem. Let ##f,f_1,\ldots, f_n:X\to\mathbb{R}## be linear functionals defined on a vector space ##X##. Theorem. Assume... -
wrobel replied to the thread Undergrad Is energy really conserved?.Gyroscopic forces do not do work. Just by definition because the gyroscopic forces are ##Q_j=\omega_{ij}(t,x)\dot x^i,## where... -
wrobel replied to the thread Undergrad How to define a vector field?.I do not understand what this means. By definition a vector field on a manifold ##M## is a function ##v:M\to TM## such that ##v(x)\in T_xM## -
wrobel replied to the thread Undergrad How to define a vector field?.The set ##B\times \{v_p\,|\,p\in B\}## contains an element ##(p',v_p)## with ##p'\in B,\quad p'\ne p##. Such a definition of a vector... -
wrobel replied to the thread Undergrad How to define a vector field?.It depends on definitions. You can take this formula as a definition. On the other hand we can start with an ordinary differential... -
wrobel replied to the thread Undergrad How to define a vector field?.You can define a vector field as follows. Assume that in any coordinates ##x=(x^1,\ldots,x^m)## in a domain ##D\subset\mathbb{R}^m##... -
wrobel replied to the thread Undergrad Is calling fictitious forces "not real" just about terminology?.And that is not all :) ##\vec F_{ab}## is parallel to a line that connects the points ##a## and ##b## -
wrobel replied to the thread Undergrad Is calling fictitious forces "not real" just about terminology?. -
wrobel replied to the thread Some thoughts about self-education.This is an offtop because I have formulated the subject of discussion: And yes if this "modern day Ramanujan" can not solve a problem...