Why is the d'Alembert's Principle formulated in terms of virtual displacements rather than real displacements in time?
89281
D'Alembert's Principle: Necessity of virtual displacements
91314
Advantages of Lagrangian Mechanics over Newtonian Mechanics
121320
Why is there conservation of kinetic energy in elastic collision and not in inelastic collision?
80967
Why are D'Alembert's Principle and the Principle of Least Action Related?
71820
Intuitive explanation of why momentum is the Fourier transform variable of position?
90325
Why use the derivative and not the symmetric derivative?
16786
Is there any case in physics where the equations of motion depend on high time derivatives of the position?
48756
Why are derivatives in interaction terms treated differently from derivatives in the kinetic term?
97466
what is the relationship between the dynamical casimir effect and virtual particles?
128695
Why do people use real values for the Wick-rotated time $\tau$?
67641
Why should field operators satisfy the classical equations of motion?
34004
Why is time evolution unitary?
68896
Why should a solution to the wave equation be finite?
18054
Is there a proof from the first principle that the Lagrangian L = T - V?
7149
Calculus of variations -- how does it make sense to vary the position and the velocity independently?
36380
Why not use the Lagrangian, instead of the Hamiltonian, in nonrelativistic QM?
15338
Why is the centre of mass displaced even when external force is 0?