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The math shows the theoretical distributions of mass, not necessary to be physically possible for any power of 1/r. So it's really a matter of discussing what actual densities are possible. You also asked to give a physical explanation to a seemingly math confusion, so you may want to specify...

yes

Thanks! I cannot seem to find quantum mechanics or lagrangian mechanics anywhere though?

Does anyone know of any "crash courses" in various physics topics such as classical mechanics, quantum mechanics, theories of relativity, field theories, etc free online? By "crash courses" I mean PDF's for example with good examples, since I learn the quickest with examples. I know it is rather...

wow... thank you. This is just what I thought, and I still heard it as potential.

Schrodinger Equation, "Potential" This is a very simple question, but I am confused. I have seen Potential and Potential Energy interchanged.. yet still referred to as potential. Is the "potential" function in the schrodinger equation really a potential function or potential energy? (units...

In terms of Kelvins, if the temperature of a sample doubles, does the energy content from heat double as well? Also, if you are passing a current through a sample, what should be the temperature vs current relation be theoretically? i.e. what is f(I) in T = f(I). Thanks,

So if the question is about where on the arm to stand to lower the lift faster, then I agree with you, you apply the same force downward. In fact, standing on the end will give more torque like you said and may squeeze the arm against the vertical part causing more friction and may make it even...

..this isn't a physics homework question.. just a wonder of mine

Relative energy of simple 2 particle system (confused!) Ok so I have a simple question which I feel I should know the answer to: Setup: Two particles of different mass.. say M and m (where M > m) are moving past each other by some constant velocity. If we view the energy of the system from...

Right ok thanks, I lost my mind there a little bit!

He mentioned something about boundary conditions, could you explain to me what you mean? What boundary conditions could make the term vanish?

I'm watching the video series on Quantum Mechanics taught by Leonard Susskind, (from Stanford). On Lecture #3, Dr. Susskind says that integration by parts is: ∫FG' = -∫GF' However from what I know integral by parts to be, there i missing a +FG on the righthand side, or something... since I...

So in my theoretical physics class my professor was reminding us ("reminding") of what "linear" means, such as a linear functions or a linear operator. He said the definition was: 1. f(ax) = a f(x) 2. f(x + y) = f(x) + f(y) Functions or operators are "linear" if they meet the above 2...

thanks very much! jonny

ehild, thank you! How do you know to do that substitution? thanks again, Jonny

But how could I get it even in terms of the integral? I need a constant of integration to solve for so y(1) = 1/2

ODE, bernoulli equation --> leads to crazy integral ! Homework Statement An Initial Value Problem, ODE (Bernoulli equation) ODE: [x^2]*y' + 2*[x^3]*y = [y^2]*(1+2*[x^2]) IV: y(1) = 1/2 Homework Equations general form of Bernoulli's equation: y' + a(x)y = b(x)*[y^n] First...

k thanks ill do that

Well it turns out I forgot how to multiply both sides of an equation. 3rd to last step I multiply half of the right side by t^2, I'm not sure how to make this thread "solved."

[SOLVED] simple ODE problem, Bernoulli's Equation Homework Statement Initial value problem: Relation: t*y' - 2*[t^2]*sqrt(y) = 4*y Initial value: y(1) = 4 Homework Equations general form of Bernoulli's equation: y' + a(t)y = b(t)*[y^n] First order, linear ODE form: y'...

My solution is that, it is an Initial value problem, (there is only one t which we care about) and with that t the argument in the natural log is positive and so u can ignore the abs value!

Integral of 1/x = ln(x)... Problem has missing absolute value!? This is an ODE problem and solution, but what I'm not understanding here is calculus based: Why does the argument to the red-boxed ln() not in absolute value signs?? ( | | ) u = cos(t) so the numerator can be negative. I am just...

I switched my major to physics from Electrical Engineering, (I am finished with freshman year and will be starting sophomore year as physics major), and many people seem disappointed with the decision. I think it has mainly to do with how much money is made; physics vs. engineering. I have to...

In the fourth video of that series, he says space and time are quantized. I thought that wasn't fully accepted yet? Am I wrong or if not, where is evidence that Planck time and distance are really the shortest?

congratulations!

Interesting, I was though asking specifically 10^1,000,000,000,000 years from now.

Nabeshin, that is what I understood from the first couple of posts and I realize I just need to study General Relativity to understand curvature fully.

The paper is supposed to be 2d, that is the point. The real fact that it is 3d, (has thickness) is irrelevant. Then your saying our spacetime has thickness in some 5 dimensions?? EDIT: I should say, the fact that a real piece of paper is 3d is irrelevant, because it's not really a piece of...

Okay.

My original question is: How can there be imaginable wormholes connecting two points in our 4d spacetime without an extra 5th dimension. The paper analogy is a 2d spacetime, connected were imagining a 3rd dimension to bend the paper into. If your saying that we never introduced a third...

dude, 2d spacetime connecting 2 points through 3rd dimension. There isn't a 3rd dimension in 2d spacetime... Are you saying there is 5th dimension in our 4d spacetime? I'm asking if that's the case.

your analogy doesn't have the same dimensions as reality, if it did why would u call it an analogy?

But your example is connecting two points in 2d spacetime isn't it, there is not 3rd dimension supposedly, yet you used it to connect the two points.

If there didn't exist a 3rd dimension you would not be able to fold them and connect the points.

Ok well, I find that to be crazy. So can it then be thought of as, scaling? For instance instead of imagining the x-axis bend into the y direction in some regions, can by the same way imagine the x-axis scaled differently at those "bent" regions?

If wormholes connect two areas in spacetime, wouldn't that require 5 dimensions? (an extra dimension past 4d spacetime.)

Yeah, but how does the process work when you see 3 other blues, (and you yourself are blue.)

But what information can possible be obtained after the first night?

Well what do you think of what I said.

Summary is below, here are the original videos. (Also, in case this problem has been posted before, you can show me the link, I could not find it.) The Original Problem: http://www.youtube.com/watch?v=rBaCDC52NOY" The Solution: http://www.youtube.com/watch?v=-xYkTJFbuM0" (I have a...

Also, is there a connection between Frame-Dragging and inertia?

but that bothers me you said: "The laws of physics are the same in both coordinate systems." Then how are centrifugal forces explained in the "rotating" frame?

A very important idea in General Relativity is, same laws in all reference frames. How does that work in rotating reference frames? Jonny

[Neutrinos] are not composed of quarks and therefore don't have a strong interaction. If you want to know why they don't collide due to gravity (lol) look https://www.physicsforums.com/showthread.php?t=406212". EDIT: I'M SORRY, I THOUGHT YOU SAID NEUTRINOS, NEUTRONS are composed of quarks...

Well, you have the electromagnet force repelling them, and the strong force keeping them together. I once wondered why the nucleus doesn't explode from all the electromagnetic repulsion (all the protons in the nucleus are positively charged) but the explanation is the strong force keeps them...

Ok thanks, I subject I will be studying not too far from now.

Ok so I am asking two things here. One is, if entropy supposedly always increases, how does that fit with the big bang? The highly dense ball of all matter in the universe mashed together in the beginning seems to have high entropy; where is the organization?? Second, why does it seem time...

Yeah that is just what I thought! Very interesting physics!

Actually I wonder the same. I believed infinites only exists in concept, but now you remind me of how a black hole has infinite density. Any more knowledgeable comments on this?