Recent content by kuruman

Observers at separate locations moving relative to each other just can't look at each other's clock and decide whether they run slow or fast. The best they can do is to communicate with each other by radio at the speed of light and report to each other what their onboard clock reads. However...

I came across this item on Snopes debunker. It originally appeared on Instagram. Quite fascinating and amusing for a physicist, but not lame enough to be posted on "Physics Lame Jokes." Here is the text minus the ads. Note that it's supposed to happen today :eek: On August 12, 2026, the...

What does that mean? The (blue) drawing in post #1 clearly defines the latitude angles of points 1 and 2 as ##\lambda_1## and ##\lambda_2.## Points 1 and 2 are shown joined by an arc on a great circle that, in general, is neither a circle of latitude nor a circle of longitude. That's all that's...

Where did the numbers come from? You should post the problem exactly as was given to you. Also, these numbers that you show do not produce the answer that you quote. Redo the calculation, preferably on a spreadsheet, where you can easily troubleshoot what you are doing.

Why do you think you are missing something in the formulas?

And the reason is that KVL is ##\oint \mathbf E\cdot d\mathbf l = 0## in disguise. Electric fields due to induced voltages are notoriously non-conservative. Disclaimer: I have not watched the video because my laptop's speaker in inoperative at the moment.

Yes, that is what I mean. The die is clearly spinning on top of the piece until the player stops it and rolls again. It is definitely not in static equilibrium. The OP is mistaken.

OP has provided the time of the event as 3:27:44. I have been playing backgammon for more than sixty years and I have seen this happen quite a few times but not for that long.

Yes, usually the "Additional Problems" at the end of a chapter combine topics and concepts presented in more than one sections of the same chapter and often require understanding of previous chapters. I would say do about 3-4 problems from each section and then try a couple of additional...

Try to solve the problems pertinent to that section. Some textbooks have rankings of difficulty. Choose the "hard" ones, usually near the end of the list of problems, that are not merely "plug and chug". Can you do them? If not, find out what it is that you missed or misunderstood that...

I have used all three in the calculus-based introductory courses that I taught at university level and found them all satisfactory. My opinion is that if you master all the material in any one of them, you have gotten the background you need to move on beyond the introductory level. Also, as...

Agreed. However, OP's question was about position and momentum.

As explained to me in QM class decades ago, the uncertainty principle is inherent in the wave-matter mathematical superposition. Expectation values, variances and "many measurements" are peripheral to this basic idea. How so? The figure on the right is lifted from the link in post #10. At the...

(Emphasis mine) As far as I know, the only experimental apparatus that can make a theoretical measurement is found in a thought experiment. You might find this reference helpful for visualizing (theoretically) the tradeoff between position and momentum measurement.

You can write your relevant equation twice, for each of the given pairs ##(x_1,v_1)## and ##(x_2,v_2)## to get a system of 2 equations and 2 unknowns, ##A^2## and ##\omega^2##. Solve the system the usual way to find the unknowns, the order doesn't matter. I checked your value for ##\omega##...