Recent content by DavidSullivan

Why would the current be infinitely large? There are a fixed number of electrons in the capacitor and they must move some distance to discharge. Their speed is bound by the speed of light, so some time must elapse. So the current should be REALLY BIG, but not infinite. Now saying I'm right...

My experience - Wikipedia is worthless if you're trying to learn something of any complexity. If you already know it, but have forgotten the formula's,etc., it can be right handy.

This concept is already in use at the macro-level in piezoelectric microphones. So, it won't cool your beer but you can rock with it! :biggrin:

Regarding the direction of the current: a current can be created using positive or negative particles. By historical convention the direction of current is determined by the movement of positive charges. Because electricity is the movement of (negative) electrons, the current "flow" is opposite...

Go to a bookstore and thumb through it. If you can knock out all 3,000 problems "plugging and chugging" you're ready to start your masters thesis in physics! -David

A to B - like Doc said, its the distance between the initial and final positions. All the bounces can be ignored. -David

Go to Amazon and search “Schaum’s Physics” and have your folks buy you a book. I have the “3000 Solved Problems..” and find it invaluable. They work from simple to hard in each category and solutions to all problems are given so you can learn if you get stumped. (Note – you need to cover the...

You're right - most artillery pieces in WWII used shells with a fixed charge, so range was established by varying the angle of the barrel. I think you could vary the charge used on a mortar, however.

The displacement in this case is the length of the hypotenuse of the triangle in the picture. Given the angle (30 deg.) and the vertical displacement (15m) you can find the total displacement. Here's a good overview if you don't understand displacement: http://physics.info/displacement/ -David

I have a question regarding this discussion, which might get at the crux of what Wayne is asking. Correct me if I’m wrong Wayne, but I don’t think he’s asking about the average force of the system as a whole (person, weights, and gravity), but specifically about the average force of the...

I don't know - I'm not a physicist and simple questions in physics seem always to have long and difficult explanations. I found the explanation in the FAQ to be a good conceptual starting point and should narrow your search if you chose to continue digging. Good luck! -David

Photons have relativistic mass. See the FAQ here on the forum: https://www.physicsforums.com/showthread.php?t=104715-David

Agreed - I'm not trying to infer any relationship between the aether of old and space-time beyond t-s seeming to act as a "medium" of sorts. -David

Is it wrong to think of the time-space continuum as an "ether" of sorts? If gravity can warp the t-s-c such that the path of light is changed, doesn't that mean it is "something?" And doesn't electric and magnetic fields, with their action-at-a-distance, also tend to imply "something"is carrying...

This is what I thought, so I'm feeling a little better. It's curious to see graphics of a photon as a squiggly little line still used so frequently. Easier than an expending sphere of energy I guess. Thanks all for the thoughtful answers, and I'm going to stay out of the way regarding the...