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Questions tagged [textbook-erratum]

For questions about possible specific errors in asker's reference material. PLEASE search for the relevant errata webpage before asking. DO NOT USE THE TAG for general critique beyond the scope of the reference.

For questions about possible specific errors in asker's reference material. PLEASE search for the relevant errata webpage before asking. DO NOT USE THE TAG for general critique beyond the scope of the reference.

251 questions
37
votes
6 answers

Is Nm the same unit of torque as mN?

A couple of days ago, I noticed that the torque unit used by my teachers is $mN$, and while reading on the internet it came to my notice that in all textbooks the official unit is $Nm$. I asked one teacher about it and he insisted that I'm wrong,…
Abdullah Alhussni
  • 499
31
votes
2 answers

Error concerning projectile motion in respected textbook?

In the textbook Fundamentals of Physics by R. Shankar of Yale Open Courses, appears the following assertion pertaining to a car driving off a cliff, which seems correct: This is exactly how long it would take to hit the ground had it simply…
Trever Thompson
  • 483
26
votes
4 answers

If an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple

Quoting from the Feynman Lectures on Physics - Vol I: The atoms are 1 or $2 \times 10^{−8}\ \rm cm$ in radius. Now $10^{−8}\ \rm cm$ is called an angstrom (just as another name), so we say they are 1 or 2 angstroms (Å) in radius. Another way to…
Lone Learner
  • 447
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24
votes
2 answers

Are all central forces conservative?

It might be just a simple definition problem but I learned in class that a central force does not necessarily need to be conservative and the German Wikipedia says so too. However, the English Wikipedia states different on their articles for…
n3rd
  • 393
18
votes
4 answers

Can spheres leaking charge be assumed to be in equilibrium?

I am struggling with the following problem (Irodov 3.3): Two small equally charged spheres, each of mass $m$, are suspended from the same point by silk threads of length $l$. The distance between the spheres $x \ll l$. Find the rate $\frac{dq}{dt}$…
user27657
  • 189
14
votes
5 answers

How can the speed of sound increase with an increase in temperature?

I was reading a textbook. I found that it was mentioned the speed of sound increases with increase in temperature. But sound is a mechanical wave, and it travels faster when molecules are closer. But an increase in temperature will draw molecules…
Ravindra Sahay
  • 177
13
votes
6 answers

Error in books of conformal field theory?

If you look at the book Conformal Field Theory (by Philippe Francesco, Pierre Mathieu and David Senechal) or the lecture notes Applied Conformal Field Theory (by Paul Ginsparg), and many other places: The conformal transformation is defined as the…
Nilanjan
  • 163
11
votes
1 answer

Hamilton's principle with nonholonomic constraints in Goldstein

I am studying from Goldstein's Classical Mechanics, 3rd intl' edition, 2013. In section 2.4, he discussed Hamilton's principle with nonholonomic constraints. The constraints can be written in the form…
radi
  • 111
9
votes
3 answers

I Do Not Understand a Textbook Example: Calculating Voltage Across a Resistor

I am reading Agarwal and Lang's Foundations of Analog and Digital Circuits for self study, and I do not understand one of their illustrated examples (specifically, example 2.14). They present this circuit and claim $v = 0.5$ V. If I were to use a…
clo_jur
  • 209
9
votes
2 answers

Does an elastic massive hanging chain take the shape of a parabola?

This is a problem in "Differential Equations: A Modern Approach with Wavelets" by Krantz: If the length of any small portion of an elastic cable of uniform density is proportional to the tension in it, then show that it assumes the shape of a…
user489562
  • 191
9
votes
1 answer

Charge structure of the neutron

David Griffiths’ book on elementary particles says that the neutron is positive at the center and edges, negative in between. (Introduction to Elementary Particles, Wiley, 1987, p. 21). But Wikipedia disagrees, saying the opposite, with what seems…
Mark Dominus
  • 2,727
9
votes
1 answer

Electron in the proximity of a magnetic monopole

I am puzzling about an exercise in the book "Electromagnetic Theory" by Ferraro (p.543). An electron (mass $m$, charge $-e$) in a monopole magnetic field $\vec{B}\left(\vec{r}\right)=g\frac{\vec{r}}{r^3}$ has due to the Lorentz force…
Andy
  • 393
7
votes
2 answers

C, T, P transformation mistakes in ``Peskin&Schroeder's QFT''?

I suppose the right way to do C (charge), T (time reversal), P(parity) transformation on the state $\hat{O}| v \rangle$ with operators $\hat{O}$ is that: $$ C(\hat{O}| v \rangle)=(C\hat{O}C^{-1})(C| v \rangle)\\ P(\hat{O}| v…
wonderich
  • 8,086
7
votes
2 answers

Does the kaon participate in the weak interaction?

I'm looking at a physics textbook for A-level and in the book it states that kaons are only affected by the strong force and the electromagnetic force. Isn't this incorrect? Aren't kaons affected by the weak force as well?
S Paul
  • 109
7
votes
5 answers

Does this question have two answers correct?

A simple pendulum (whose length is less than that of a second's pendulum) and a second's pendulum start swinging in phase. They again swing in phase after an interval of $18$ seconds from the start. The period of the simple pendulum is (A) $0.9$…
Righter
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