User mike stone

80 votes

Accepted

Why does rainwater form moving waves on the ground? Is there a name for this effect?

answered Mar 19, 2017 at 13:20

71 votes

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Why does a body always rotate about its center of mass?

rotational-dynamics reference-frames

answered Feb 12, 2017 at 16:26

69 votes

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Why doesn't a mercury thermometer follow the rules of volume dilatation?

thermodynamics physical-chemistry heat-conduction

answered Nov 11, 2020 at 21:32

54 votes

Can a battleship float in a tiny amount of water?

pressure fluid-statics buoyancy

answered Dec 16, 2018 at 14:13

53 votes

What is a joule? I find the definition confusing

energy work definition si-units metrology

answered Mar 24 at 13:43

30 votes

Why do physicists use the Bra and Ket notation when mathematicians tend not to?

quantum-mechanics hilbert-space notation linear-algebra

answered Apr 28, 2021 at 21:33

29 votes

Triviality of interacting QFT

quantum-field-theory renormalization spacetime-dimensions interactions

answered Jun 5, 2020 at 22:10

28 votes

Accepted

Why does it take so long for a gas to reach a thermal equilibrium?

thermodynamics statistical-mechanics kinetic-theory

answered May 3, 2021 at 17:01

25 votes

Must observables be Hermitian only because we want real eigenvalues, or is more to that?

quantum-mechanics hilbert-space operators complex-numbers observables

answered Apr 24, 2021 at 12:08

24 votes

Why is the mechanical advantage 8 and not 4 in this pulley system?

homework-and-exercises newtonian-mechanics string

answered Jul 19, 2021 at 21:40

21 votes

Why do images not appear inverted when looking directly through a pinhole camera?

optics camera

answered Apr 10, 2021 at 12:06

20 votes

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Is the right hand rule a trick to avoid tensors?

angular-momentum vectors angular-velocity

answered Sep 8, 2018 at 15:24

20 votes

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Lorentz invariance of Maxwell's equations in matter

electromagnetism special-relativity inertial-frames refraction lorentz-symmetry

answered May 8, 2019 at 15:44

19 votes

Approximating an expression for a potential

homework-and-exercises electromagnetism electrostatics error-analysis approximations

answered Aug 4, 2019 at 12:40

19 votes

Non-unique zero function in the function space (Hilbert space)

quantum-mechanics hilbert-space mathematical-physics integration mathematics

answered Apr 20, 2020 at 17:30

19 votes

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If frequency of photons is a continuous spectrum, wouldn't the chance of a photon having the exact right frequency to excite an electron be zero?

particle-physics waves visible-light photons probability

answered Apr 14 at 17:18

15 votes

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Misunderstanding of the magnetic field

electromagnetism magnetic-fields maxwell-equations

answered Jun 7, 2020 at 18:15

15 votes

Is continuity of the wavefunction "put in by hand" for the Dirac delta potentials?

quantum-mechanics wavefunction mathematical-physics schroedinger-equation dirac-delta-distributions

answered Nov 15, 2020 at 20:06

14 votes

Are the speed of sound and water ripples' speed the same?

waves acoustics water speed

answered Feb 27, 2021 at 20:30

14 votes

Can you make a laser without cavity, if you have a pump strong enough? I think no, but is my reasoning correct?

laser laser-cavity

answered Apr 12, 2020 at 13:20

13 votes

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Can a Hermitian operator $A$ bring a wavefunction $|\psi \rangle$ out of Hilbert space?

quantum-mechanics hilbert-space operators wavefunction

answered Sep 6, 2019 at 14:41

12 votes

Complex conjugate and transpose "with respect to a basis"

hilbert-space operators complex-numbers linear-algebra

answered Sep 7, 2019 at 16:14

12 votes

Green's function on torus

differential-geometry string-theory conformal-field-theory greens-functions dirac-delta-distributions

answered Jan 5, 2020 at 15:54

12 votes

Accepted

Chirality of the Electromagnetic Field Tensor

group-theory group-representations chirality duality

answered Sep 20, 2018 at 14:37

12 votes

How can Cooper pairs form in zero temperature, if there are no phonons?

condensed-matter superconductivity phonons

answered Dec 1, 2020 at 13:08

12 votes

Do spinors form a vector space?

vectors group-theory definition representation-theory spinors

answered May 16, 2021 at 13:57

12 votes

Do elementary particles at rest produce magnetic fields?

electromagnetism magnetic-fields quantum-spin

answered Oct 25, 2020 at 19:19

12 votes

Can sound waves deform (curl brake) like water waves?

waves acoustics

answered Mar 11 at 22:58

11 votes

If a person drops a briefcase in an elevator and it does not fall to the floor, what is the elevator's aceleration?

newtonian-mechanics reference-frames acceleration free-body-diagram

answered Nov 22, 2021 at 0:39

11 votes

Are eigenfunctions of $E$ also eigenfunctions of $p$?

quantum-mechanics energy hilbert-space operators momentum

answered Nov 10, 2020 at 22:43

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1,428 Answers

Why does rainwater form moving waves on the ground? Is there a name for this effect?

Why does a body always rotate about its center of mass?

Why doesn't a mercury thermometer follow the rules of volume dilatation?

Can a battleship float in a tiny amount of water?

What is a joule? I find the definition confusing

Why do physicists use the Bra and Ket notation when mathematicians tend not to?

Triviality of interacting QFT

Why does it take so long for a gas to reach a thermal equilibrium?

Must observables be Hermitian only because we want real eigenvalues, or is more to that?

Why is the mechanical advantage 8 and not 4 in this pulley system?

Why do images not appear inverted when looking directly through a pinhole camera?

Is the right hand rule a trick to avoid tensors?

Lorentz invariance of Maxwell's equations in matter

Approximating an expression for a potential

Non-unique zero function in the function space (Hilbert space)

If frequency of photons is a continuous spectrum, wouldn't the chance of a photon having the exact right frequency to excite an electron be zero?

Misunderstanding of the magnetic field

Is continuity of the wavefunction "put in by hand" for the Dirac delta potentials?

Are the speed of sound and water ripples' speed the same?

Can you make a laser without cavity, if you have a pump strong enough? I think no, but is my reasoning correct?

Can a Hermitian operator $A$ bring a wavefunction $|\psi \rangle$ out of Hilbert space?

Complex conjugate and transpose "with respect to a basis"

Green's function on torus

Chirality of the Electromagnetic Field Tensor

How can Cooper pairs form in zero temperature, if there are no phonons?

Do spinors form a vector space?

Do elementary particles at rest produce magnetic fields?

Can sound waves deform (curl brake) like water waves?

If a person drops a briefcase in an elevator and it does not fall to the floor, what is the elevator's aceleration?

Are eigenfunctions of $E$ also eigenfunctions of $p$?