Explain — 398 discussions

I've been reading my physics book and there they derived the formula ∑τ = Iα where τ is torque, I is moment of inertia of a rigid body and α is the angular acceleration. They did by taking an arbitrary particle on the rigid body with an applied external force tangent to the rotation. τ1 = Ftan *...

"How it can be explained mathematically by dP/dV = -gammaP/V

Homework Statement I am trying very hard to understand voltage. I am a second year engineering student in a physics II class. I am having trouble grasping the concept of voltage. Could you guys please help me out with a few questions. Please correct me if I am wrong, but isn't voltage the...

Γ(n) = ∫x→∞ tn-1 e-t dt?

Here is a link to a lecture by Scott Aaronson. http://www.scottaaronson.com/democritus/lec9.html About half way in the lecture he talks about the "qubit". In that section he introduces a 2x2 unitary matrix which rotates a vector by 45°. He applies that transformation to the state |0>. When he...

Hey! I am going to do a presentation about the bootstrap paradox in a few weeks and I need some help. I understand what the bootstrap paradox is but I need some help to sum up the theory so that i becomes easy (or at least easier) to understand. If you have any examples or facts that's fun...

I am trying to find an animation (from the internet) explaining the intricate balance of heavenly bodies (stars, planets, satellites, comets etc) in their own orbits. What happens if there is a sudden change in anyone of characteristics of those heavenly bodies. Is a small perturbation in...

This is a plot for understanding the stability of flows through the orr sommerfeld equation. However, I find it really hard to understand. The plot by itself is a little weird, what is it trying to convey?

How is the JAXA tether experiment supposed to work in space? I hear the words, "it will act as a drag and cause early de-orbit". However, the tether is orbiting with the satellite (ATV) - same orbit, same speed (velocity), but with less mass and less drag profile than the Host Transfer Vehicle...

Hi! My first post! I was wondering if anyone could explain this equality in words? I do not understand how the k became a constant (2) on the right side?Best Flippa

Homework Statement This is the definition I got from my book: "A crucial classification of differential equations is whether they are linear or nonlinear. The ordinary differential equation ##F(t,y,y',...,y^{(n)})=0## is said to be linear if F is a linear function of the variables ##y...

Hey guys, I'm wondering why is distance squared in these equations? Like F=Gm1m1/r^2 and F=kQ1Q1/r^2 Thanks

in my physics class we have to create a device that will make an egg not break after being dropped from a second story window. my idea was to take a strength training resistance band and use it like a bungee jumping cord and have the egg drop to the bottom without breaking. what are the formulas...

I learned in Analytical Mechanics: "Emmy Noether's theorem shows that every conserved quantity is due to a symmetry". The examples I learned where conservation of energy as symmetry in time and conservation of momentum as symmetries in space. Now I wonder, do universal constants are also due to...

I have found about Strukturbericht and got some information. But I don`t know what these number means. I heard that Mn_5Ge_3 is a D8_8 type structure. I already found that D means A_m B_n compound. But I can`t find anywhere what the number mean.

Hello all, I am attempting to teach myself some basic electrical knowledge, but I am slow to start. I understand what resistors do and how capacitors store a static electric charge ect... The question is, can someone explain to me the flow of electricity from beginning to start of this circuit...

Homework Statement [/B] List two postulates of special relativity and then in your own words explain how these two statements are synthesized in Einstein's theory. Homework Equations 1. The laws of physics are the same in all inertial reference frames. 2. Light propagates through a vacuum...

Homework Statement I don't understand the cuts or the views. For example if we make a horisontal cut, which view we should show? http://1.1m.yt/UJasa7v.jpg Homework EquationsThe Attempt at a Solution I have in the book an example that if we make a vertical cut we show the upper view (view...

Homework Statement Referencing to the gross and fine structure, explain how the energy diagrams differ for Hydrogen and Sodium. What effect does this have on the observed spectra? Homework Equations Sodium config: 1s21s22p63s1 Hydrogen : 1s1 The Attempt at a Solution I think that the diagram...

Hello, I do have an question about electromagnetic fields (EMF). Yesterday I conducted an small experiment after stumbling onto videos on YouTube about EMFs and the alteration of human biology. Those stunned me, because I had no idea electromagnetic fields could alter human physiology. On...

Screenshot below -Thanks

Homework Statement Homework Equations N/A The Attempt at a Solution I can't even understand the question and what is happening in the situation :(

I'm working out an impedance matching problem from a textbook (it is not part of any coursework) and I am trying to figure out how they get the 315 term in the polar coordinates below. Z = (XC*RL)/(XC+RL) = (-j333*(1000))/(-j333+1000) = 315 , -71.58* = 100 -j300 ohms I calculated that...

I'm trying to understand the physics of reflection to better draw objects. Normally, you see the reflection of a light source on metallic surfaces where the angle of incidence can equal the angle of reflection. This should reflect an image of the source that is approximately equal in size to how...

can dark matter explain Tully-Fisher relation, or is modified MONDlike gravity a better explanation for this? new paper The Radial Acceleration Relation in Rotationally Supported Galaxies Stacy McGaugh, Federico Lelli, Jim Schombert (Submitted on 19 Sep 2016) We report a correlation between...

I was walking outside this morning and saw an interesting color effect in the ground cover. Parts of some leaves were illuminated by the sun and looked as expected (left side of image) but when I walked a bit further down and looked back the illuminated areas appeared pinkish (right side of...

[Mentor's note: This thread started as a fork of https://www.physicsforums.com/threads/does-the-electron-really-spin-720-degrees.887917.] If you cannot translate the math to language, you are doing something very, very wrong. You are fundamentally at odds with the reality that physics is...

While in class, my Thermodynamics professor came up with an interesting fact, that neither I nor my colleagues were ever aware of: While you may have heard that friction influenciates the movement in Newtonian Mechanics, no one really knows what friction is. And so I have been wandering why it...

Homework Statement http://imgur.com/tQR7Jdt Homework Equations xc= vm/im The Attempt at a Solution http://imgur.com/a/RwIUA Can someone please explain where did they get that pi/2 ? did they integrate 2cos(10t)or something? Thanks

Not resorting to religion, how does apparent ordered structured complexity materialize in the universe? I want to be honest here, so I will let it be known. I'm also interested to know how this forum, which is highly censored main stream view only, deals with a topic mainstream has little to...

Hi, Sorry this is an unusual thread and question, but I figured people here might be able to explain the physics of what is going on in this image I came across a few images of an underground music club in Berlin where an image of stained glass art you would find in a church is being projected...

What is the desired outcome and why in space? http://gbtimes.com/china/china-launches-worlds-first-quantum-science-satellite-jiuquan

Homework Statement I've been looking at examples of motion derivations for my class, and it's honestly just very confusing. I heard Dynamics should prep you for this but I must have had a very poor course because we never had to understand geometry and physics to this degree... Homework...

Homework Statement i am working through this question, the final bit i am struggling with, describing what each bit of the circuit does. tying to understand what is going on. Looking at fig 1b I have identified a bridge rectifier, and the zener diode. I am reading up on these so i am not...

Can someone explain to me some of the key observations Helmholtz equation cannot explain and why that is so? Thanks!

Planck proposed the ad hoc assumption that the radiant energy could exist only in discrete quanta which were proportional to the frequency. This would imply that higher modes would be less populated and avoid the uv catastrophe of the Rayleighs law.

So far, I have only seen about 3 LIPUS (Low Intensity Pulsed Ultrasound) devices that are commercially available. The one that I am looking at right now is made by Bioventus Global and it is called Exogen.The " http://www.exogen.com/us/patient-resources ", on Bioventus Global website, states...

Suppose two rigid circular coins are lying on top of each other. A horizontal force on the top coin is applied. So, I think there are two possible scenarios: 1. Both move together with common acceleration (if friction between them is strong) 2. Only the top coin slips over the bottom (if...

Homework Statement On the right bottom side ,when the switch is closed the equation is given V(EG)=+V+V(FG) The photo is attached Homework Equations Concept The Attempt at a Solution What is the difference between the back emf in the inductor and the p.d across the inductor? I think the...

Homework Statement In describing a wheel's circular motion: "Circular motion arises purely from the resistance of the ground upon which it is applied…this resistance is equal to the force which draws the wheel in the right line" Homework Equations F=m(v^2/r) The Attempt at a Solution Is this...

Homework Statement Explain why a saucepan has a plastic or wooden handle. Homework Equations Maybe Ko = oC + 273o The Attempt at a Solution I tried looking at a book. I also know a saucepan has a plastic or wooden handle because of conducting heat. I think.

A light particle solution to the cosmic lithium problem Andreas Goudelis, Maxim Pospelov, Josef Pradler (Submitted on 29 Oct 2015 (v1), last revised 24 May 2016 (this version, v2)) We point out that the cosmological abundance of 7Li can be reduced down to observed values if during its formation...

I was told in special relavity that f=ma does not always hold true so using the f=delta p/delta t is better. So why is that? They said it had something to do with relativistic mass, at least when traveling at 99.9% of the speed of light.

Is it possible to explain themain ideas of GR without complicated math? In particular, what is the relation of current model of universe (FLRW) and GR? what is the difference between spacetime and universe, spacetime is surely curved and universe can by flat at same time? both mass and energy...

Homework Statement Homework EquationsThe Attempt at a Solution

Hello, I'm currently writing a report on young's double slit experiment, and I've used the equation nλ/d = x/L and I was wondering if someone could explain the question? I know how it works, and how to solve for lambda, but could I have some more detail into why it works? For example, why can...

So I'm sitting at my dest playing with my greeen laser pointer pointing it at different things. In all cases I see a green dot and its reflection off other objects. Except when I point it at a pink hilighter standing upright on my desk. Instead of a green dot I see a yellow dot. That dot...

And how we use it to calculate distances from stars to the earth.Thank you

widely reported in the news is a second observation of 2 black holes gravitational waves. also reported are its implications Science World Report-Jun 15, 2016 Astronomers have reportedly started to think that dark matter could be made up of primordial black holes. According to Alexander...

In our apartment, for the last few months, my wife and I are being puzzled by strange sounds coming from the dining area while we remain in the bedroom at night. The first time we heard, I was quiet. Then my wife said, "Did you hear that?" So, it was no hallucination whatsoever. It is a distinct...