# Search results

1. ### Calculate Resonance Frequency of a Molecule

I remember calculating the resonance frequencies of a water molecule using classical mechanics. We use Lagrangian mechanics and modeled each atom in the molecule as a point mass, and we assumed the force between each atom was proportional to their separation (like Hooke's law). I imagine...
2. ### How to measure berry phase?

I'm looking at D. J. Griffiths' intro to QM. I regards to Berry's phase he says one could split a particle beam into two, have one part go through an adiabatically changing potential, and recombine the beams and measure the new wave function (definitely open-ended). According to the Feynman...
3. ### Help for quickest and clearest route for differentiation question

Try substituting z = x^(1/2), then cast the result into the form az^2 + bz + c = 0.
4. ### US running out of places to store money

Last time I paid in coins it was \$2.75 in quarters, hardly a burden to count, but the cashier paused and gave me an extended dirty look. I don't use coins anymore because I don't want to leave the store as angry as I did that day.
5. ### Confusion with understanding derivatives in respect to

A derivative can be thought of as a rate of change of a variable. The expression dx/dy in English is "the derivative of x with respect to y." What this means is that we are looking at the rate at which x changes when y changes. In physics you might be interested in an object's speed. If the...

What is X exactly? By the way, common sense will lead you to dark alleys and beat you to death in physics.
7. ### Pondering an old quote from Maxwell

During Maxwell's time, the theory of vector calculus was not well-established. Also, much of the vocabulary of his day is obsolete. I tried reading Maxwell's "Treatise on Electricity and Magnetism" and I found that it took way too much concentration to follow his ideas (but it made me...
8. ### Normal force: Why not conservative?

In my head I'm imagining a block glued to a surface that is free to rotate from an axis some distance away from the block. If the surface rotates 360 degree, it is back where it started, but not before doing some work on the block. I'm used to thinking of conservative forces in terms of the...
9. ### Maxwell's A Treatise on Electricity and Magnetism

Out of date indeed. Charges in the book are called resinous or vitreous instead ofnegative and positive, and several of the concepts we have today are nowhere apparent (or at least not directly mentioned). The concept of the electric field is not directly mentioned in the book. As a matter of...
10. ### Wave Collapse and Degenerate States - A Quick Question

Let's say you have some quantum particle whose eigenvalues for some observable Q are either degenerate or non-degenerate. If you measure the observable and find it to be in a non-degenerate state, then you know that the wave function has collapsed onto this state. Now if you measure the...
11. ### MIT series on Electromagnetism

I was just about to post this haha. There are also introductory mechanics lectures 8.01 at: http://www.youtube.com/view_play_list?p=F688ECB2FF119649&search_query=MIT+8.01" and vibrations and waves 8.03: http://www.youtube.com/view_play_list?p=854AA255B15C574C&search_query=MIT+8.03"
12. ### Maxwell's A Treatise on Electricity and Magnetism

Maxwell's "A Treatise on Electricity and Magnetism" I bought this book as a supplement to my electromagnetism I class, but the moment Maxwell goes into anything mathematical, I'm lost. The lack of illustrations and reference to many out-dated terms makes the book hard to follow. The book is a...

My university offers a "physics engineering" degree which acts as a kind of hybrid between science and engineering. Perhaps your college offers something like this. The best bet is to talk to an academic adviser. I hope everything works out for you.
14. ### Does anyone have any recommendations as to how to assign error to this?

I once had a lab assignment in which we used FFT's to measure the speed of sound. We took the full width at half maximum (in frequency space) as the error estimate in our measurement for the frequency.
15. ### Drawing the short straw

1 In theory, the only condition required for the water in the straw to hover is that the force pushing the water down (mg) is equal to the force pushing the water up (PA) where P is the pressure difference between the top of the water and the bottom. Now for a circular lake of diameter...

May I suggest taking some flat material (the surface) and poking a hole in it so a string may be fed through the hole vertically. One end of the string could drag something across the surface, the other end could be connected to some weight which pulls the other end with some known force (F=mg)...
17. ### Momentum and Angles

Did you learn about center of mass? I'm sure your textbook probably has a section on it. The momentum of the system is the same as the momentum of the center of mass of the system.
18. ### Laplace Equation problem

A generalization of Laplace's equation is called Poisson's equation, which shows that the Laplacian (div dot grad) of P (in this case the electric potential) is proportional to the charge density enclosed by the region under consideration. If there is no charge in the region, then the Laplacian...
19. ### Who thinks they are smart?

Absolutely. Have you ever pulled off a 360 on a cart? Epic.
20. ### Who thinks they are smart?

Agreed. I think the mind is limitless to the field that interests it. The man that bags my groceries may know more about gathering carts than I could ever hope to understand about the motion of classical particles.
21. ### Projectiles, 2D Motion, Bullet falling

Maybe you have a 50% because you've convinced yourself that you are dumb. We aren't even halfway through the semester here, and hard work proves to be a miracle maker. I start almost every semester with 65% or less on tests in my classes, but I have managed to turn every one of those 60%'s into...
22. ### Microscope calculation

If you have any doubt as to what the answer is, CONVINCE YOURSELF. What if you were a ridiculously tall Titan of 100ft whose naked eye could only focus on something as close as 4 inches away? Let's say some funny fellow Titan created a device (we'll call it a microscope) which could focus on...
23. ### Projectiles, 2D Motion, Bullet falling

The bullet falls at a constant acceleration (gravity = 9.8m/s^2). Its horizontal velocity is constant, since it does not accelerate due to gravity. A little birdie seems to have told you the horizontal velocity of the bullet (tweet tweet, it's 340 m/s.) How does its horizontal position D relate...
24. ### Microscope calculation

Good, now if the specimen takes up a quarter of this space, how big is it?
25. ### Lenz's Law & Magnetics

Lenz's law is kinda hard to picture, even to me after getting an A in intro E&M. The way I deal with it is the following: Think of an arrow pointing in the direction of the magnetic flux through a loop. Using the right hand rule (please use your right hand, It makes me feel anxious and sad when...
26. ### Vectors, Forces Accelerating a Train

It still disgusts me how a lot of physics textbooks make students do numerical calculations instead of general solutions. That aside... Both questions are talking about a CHANGE IN VELOCITY. What is the change in velocity called? Hint: It's called acceleration, shhhh don't tell. For question...
27. ### Lenz's Law & Magnetics

(b) The induced current in loop 2 is created by a >>>>>CHANGE<<<<< In the magnetic flux through loop 2. Is the magnetic flux through loop 2 changing? (c and d) If there is a current in loop 1, and a current in loop 2, then how is the force between the two loops related to the direction and...
28. ### Who thinks they are smart?

I don't find myself to be smart, but I do believe I have worked hard to appear intelligent. Whether this makes me more or less arrogant than the person that finds him or herself to be VERY SMART is still a question that is up in the air. If you were to test my knowledge on history, politics...
29. ### Recommend me a calculus based physics text?

I started college as a math major and my physics class used Serway's book, but when I switched to physics I was required to purchase a new book (Sear's and Zemansky's University Physics, 12th ed.). The material covered in each book is nearly identical, though Sear's and Zemanksy's goes into more...
30. ### Is electric electrons and protons?

Yeah, Ben Franklin was the man that decided that electrons were to be considered the "negative" charge, and since there weren't any well understood means of finding out which charges were actually moving in circuits, he had a 50/50 chance of making the sign convention simple. Unfortunately, most...