User Physiks lover

39 votes

5 answers

8k views

Does a photon in vacuum have a rest frame?

asked Oct 21, 2011 at 17:52

29 votes

8 answers

8k views

Why is there a $\frac 1 2$ in $\frac 1 2 mv^2$?

newtonian-mechanics energy work

asked May 5, 2012 at 21:52

10 votes

4 answers

831 views

Why isn't there a limit for a Euclidean rotation, as for a Minkowski rotation?

special-relativity

asked Jun 12, 2014 at 21:26

7 votes

2 answers

651 views

What experiments compete with BICEP 2, and when are their results expected?

cosmology experimental-physics cosmological-inflation cosmic-microwave-background

asked Mar 17, 2014 at 23:33

7 votes

2 answers

351 views

How does Dirac define the representative of $\{\langle\phi\frac{d}{dq}\}\psi\rangle = \langle\phi\{\frac{d}{dq}\psi\rangle\}$

quantum-mechanics operators hilbert-space

asked Dec 15, 2014 at 1:04

7 votes

8 answers

3k views

Is Einstein's 1916 General Relativity paper a recommended way to start learning about the subject?

general-relativity

asked Sep 1, 2011 at 17:55

6 votes

2 answers

4k views

Is the change in kinetic energy of a particle frame independent?

special-relativity classical-mechanics energy inertial-frames

asked Apr 5, 2012 at 23:11

6 votes

1 answer

183 views

Why isn't EM radiation from an accelerated charge time reversible?

electromagnetism electromagnetic-radiation classical-electrodynamics cpt-symmetry

asked Jan 31, 2020 at 20:42

5 votes

2 answers

198 views

Do Maxwell's equations contain any information on the time evolution of the current density $J$?

electromagnetism lagrangian-formalism conservation-laws maxwell-equations time-evolution

asked Jul 11, 2020 at 1:11

5 votes

2 answers

3k views

Is (0,0,0) an undefined vector?

vectors

asked Nov 11, 2011 at 21:50

5 votes

3 answers

2k views

Explanation for $E~$ not falling off at $1/r^2$ for infinite line and sheet charges?

electrostatics electric-fields gauss-law coulombs-law

asked Jul 27, 2012 at 0:34

5 votes

4 answers

2k views

Are the principles of space-time homogeneity and Isotropy independent of one another?

general-relativity spacetime symmetry differential-geometry

asked Dec 20, 2012 at 1:02

5 votes

2 answers

153 views

Should the eigenkets be weighted in $|P\rangle = \sum\limits_{r}|\xi^r\rangle$?

quantum-mechanics hilbert-space superposition

asked Oct 12, 2014 at 23:56

4 votes

4 answers

9k views

Is the electric field zero inside an ideal conductor carrying a current?

electromagnetism electric-fields

asked May 20, 2012 at 17:16

4 votes

1 answer

309 views

Is there a Newton's third law for the em field?

classical-mechanics classical-electrodynamics

asked Oct 25, 2011 at 22:26

4 votes

1 answer

4k views

Proofs that every professional physicist should know [closed]

soft-question big-list

asked Nov 4, 2011 at 14:55

3 votes

1 answer

4k views

Problems that Lagranges equations of the 1st kind can solve whereas the 2nd kind can't?

classical-mechanics lagrangian-formalism

asked Nov 19, 2011 at 22:41

3 votes

1 answer

2k views

Can relativistic kinetic energy be derived from Newtonian kinetic energy?

classical-mechanics special-relativity

asked Apr 13, 2012 at 14:41

3 votes

3 answers

4k views

Calculate relativistic boost to COM frame from two arbitary velocities?

homework-and-exercises special-relativity classical-mechanics velocity inertial-frames

asked Apr 25, 2012 at 23:00

3 votes

2 answers

386 views

Why does a stationary force affect the conservation of momentum, but not the conservation of energy?

classical-mechanics energy momentum

asked Sep 24, 2013 at 14:46

3 votes

4 answers

220 views

Is there a space-like equivalent of the Twin Paradox?

special-relativity spacetime time-dilation

asked Oct 15, 2017 at 0:47

3 votes

1 answer

116 views

How can one define a covariant rate of change of rest mass for an extended body?

general-relativity special-relativity classical-mechanics mass mass-energy

asked Feb 23, 2019 at 16:39

2 votes

2 answers

118 views

Can an accelerated spring in static equilibrium in its rest frame have different forces at each end?

homework-and-exercises newtonian-mechanics classical-mechanics spring

asked Aug 5, 2018 at 22:38

2 votes

2 answers

106 views

Must the varied paths in the action be physically possible?

classical-mechanics lagrangian-formalism variational-principle action

asked Oct 5, 2018 at 23:35

2 votes

3 answers

95 views

Does a spring's $k$ affect the acceleration of a coupled mass?

newtonian-mechanics classical-mechanics energy spring

asked Oct 30, 2018 at 1:15

2 votes

2 answers

131 views

QM probability density function without Born's rule, invariant to wave-function phase

quantum-mechanics hilbert-space wavefunction probability born-rule

asked Jul 31, 2019 at 0:07

2 votes

3 answers

831 views

Can the Euler-Lagrange equations be derived from an infinitesimal Principle of Least Action?

lagrangian-formalism variational-principle

asked Oct 17, 2012 at 14:59

2 votes

1 answer

151 views

Why does Dirac write $\langle\xi'|\overline{f(\xi)} = \overline f(\xi ')\langle\xi'|$?

quantum-mechanics notation

asked Oct 5, 2014 at 15:04

2 votes

1 answer

91 views

How does Dirac show that $\langle B|\bar{\bar{\alpha}}|P\rangle\;=\; \overline{\langle P|{\bar{\alpha}}|B\rangle}\;=\; \langle B|{\alpha}|P\rangle$?

quantum-mechanics operators

asked Sep 2, 2014 at 16:59

2 votes

1 answer

121 views

If time-like paths are geodesics, what physical principle applies to space-like intervals?

special-relativity field-theory classical-electrodynamics variational-principle geodesics

asked May 27, 2015 at 18:19

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72 Questions

Does a photon in vacuum have a rest frame?

Why is there a $\frac 1 2$ in $\frac 1 2 mv^2$?

Why isn't there a limit for a Euclidean rotation, as for a Minkowski rotation?

What experiments compete with BICEP 2, and when are their results expected?

How does Dirac define the representative of $\{\langle\phi\frac{d}{dq}\}\psi\rangle = \langle\phi\{\frac{d}{dq}\psi\rangle\}$

Is Einstein's 1916 General Relativity paper a recommended way to start learning about the subject?

Is the change in kinetic energy of a particle frame independent?

Why isn't EM radiation from an accelerated charge time reversible?

Do Maxwell's equations contain any information on the time evolution of the current density $J$?

Is (0,0,0) an undefined vector?

Explanation for $E~$ not falling off at $1/r^2$ for infinite line and sheet charges?

Are the principles of space-time homogeneity and Isotropy independent of one another?

Should the eigenkets be weighted in $|P\rangle = \sum\limits_{r}|\xi^r\rangle$?

Is the electric field zero inside an ideal conductor carrying a current?

Is there a Newton's third law for the em field?

Proofs that every professional physicist should know [closed]

Problems that Lagranges equations of the 1st kind can solve whereas the 2nd kind can't?

Can relativistic kinetic energy be derived from Newtonian kinetic energy?

Calculate relativistic boost to COM frame from two arbitary velocities?

Why does a stationary force affect the conservation of momentum, but not the conservation of energy?

Is there a space-like equivalent of the Twin Paradox?

How can one define a covariant rate of change of rest mass for an extended body?

Can an accelerated spring in static equilibrium in its rest frame have different forces at each end?

Must the varied paths in the action be physically possible?

Does a spring's $k$ affect the acceleration of a coupled mass?

QM probability density function without Born's rule, invariant to wave-function phase

Can the Euler-Lagrange equations be derived from an infinitesimal Principle of Least Action?

Why does Dirac write $\langle\xi'|\overline{f(\xi)} = \overline f(\xi ')\langle\xi'|$?

How does Dirac show that $\langle B|\bar{\bar{\alpha}}|P\rangle\;=\; \overline{\langle P|{\bar{\alpha}}|B\rangle}\;=\; \langle B|{\alpha}|P\rangle$?

If time-like paths are geodesics, what physical principle applies to space-like intervals?