Confusion Definition and 1000 Threads

I am about to have a water softener installed and I thought I should learn a bit about the Chemistry involved. There is loads of advertising blurb on the Web but very little precise Chemistry. I am sure someone here can help me with this. The basic softening process is fair enough with sodium...

I am a bit confused about the energy density in an EM wave. why do we take the Peak value of E vector while calculating the energy density? Like if the E field is ##E_0 Sin(kx-wt)## what is the energy density of the EM wave(Magnetic + Electric)? is it A) ##\frac {e_0E_0^2}{2} ## or B) ##...

Why can sometimes entropy remain constant with increase of temperature and vice versa?Entropy implies transfer of heat and heat must increase with temperature.I am unable to intuitively understand.

Homework Statement State the exact value of ##y=arccos\left(\frac π 2 \right)## Homework EquationsThe Attempt at a Solution In a "typical" question, such as ##y=arccos\left(-1\right)##, I look at it like "The cosine of what angle gives the value -1?" I then see that it's π. This question...

1. The problem statement, all variables, and given/known data A parallel-plate capacitor has the space between the plates filled with to slabs of dielectric, one with constant K1, & one constant K2. each slab has thickness d⁄2, where d is plate separation, show the capacitance is? Homework...

So I understand that a capacitor consists of 2 plates separated by a distance which creates a potential difference between the plates. But I was confused, when watching this physics video it seemed to be saying that once the capacitor was fully charged, the plate closest to the positive terminal...

Hi there, I'm struggling to distinguish why the following two equations are giving distinct answers, when the question explicitly states either could be used: v=u+at v^2=u^2+ad when v=12 m/s u=0 m/s a (average acceleration)= the unknown variable d=24 m t=4s Theoretically, the two should...

Homework Statement :[/B] This is isn't exactly a problem,but actually something i don't understand in the book i was following, so there this art. about 'Principle of a Generator', whose description is given as, " A generator is an instrument for producing high voltages in the MeV range. Its...

Hi, I’m a bit confused about the definitions of corotational and Lindblad resonances. They’re given by; Corotational resonance This resonance occurs when the orbit moves at the same angular speed as the forcing. Lindblad resonance an orbital resonance in which an object's epicyclic frequency...

I have some serious issues trying to understand the idea of the spin in the context of the Stern-Gerlach experiment and would appreciate some assistance! Assuming that a homogenous magnetic field ##B## in the "North-wards" ##z##-direction, assume that there is a magnetic dipole moment ##\mu##...

Homework Statement Homework EquationsThe Attempt at a Solution a) charge induced is ##\frac{-q_i}{4 \pi r_i^2} = \sigma_i## ##\frac{q_a + q_b}{4 \pi R^2} = \sigma_R## b) field outside is ##\frac{k (q_a + q_b)}{r^2}## c)i naively applied gauss law to get field within each cavity as...

Hi everyone. I've been doing a lot of reading regarding electric potential and electric potential energy. Unfortunately, I have a lot of confusion regarding this topic, as I keep receiving different information. My main confusion is regarding the signs, positive or negative, of work and it's...

Hello, If I understand correctly, according to Kepler, a planet orbiting a star should cover a constant surface area of its ellipsoid or circular orbit per time unit, regardless of the distance of that planet to the star. I have tried to prove this by using a scenario in which a planet is...

Is mach cone the area of the shock wave or the wave front of the Mach wave? Usually the diagram for mach cone is this, However I still see some author states that the Mach cone is the shock wave. Shouldn't the shock wave be at the intersection(between the circles) and if the Mach cone is about...

Hey. Undergrad UK Chemical Physics student here. Looking for some advice when it comes to sorting out my degree path. First however. Some background info for those unaware with the degree 'system' in the United Kingdom: Most Universities in the UK have you apply for degree programs through...

Source: https://en.wikipedia.org/wiki/Irreversible_process I think I can see it mathematically but it is not very intuitive to me as it seems like there is creation of energy...

Homework Statement I am having a issue with calulating my errors for this particular experiment the reason I will detail below. I have also print sceend in the section of my lab report to show the experimental setup etc. Lab Script So in the lab during the experiment the tesla meter...

Why the negative pole of a battery is said to be of higher potential? While if we a consider a DC battery of 12V (for instance) then we have Vpn=V (positive) -V (negative)=12V whish is a positive quantity, then we should conclude that Vp>Vn in contradiction to first statement! Please illustrate...

[Moderator's note: split off from another thread since this is a separate topic.] I am confused about closed timelike curves. To say that they are possible using an exact solution to the EFEs, like the Godel metric, and that they actually correspond to something in reality is where my confusion...

Wiki here: https://en.wikipedia.org/wiki/Frame-dragging Claims that: It sounds strange. What happens if an observer is hovering in equatorial plane of the rotating black hole, few meters above the ergosphere? Now an observer starts to release a chain, very slowly. Wiki claims that a chain will...

Homework Statement this has been bugging me for a while now the angular momentum about any point p is given as ## \vec {L_p} = \vec {R_{cm,p}} \times \vec {P_{cm}} + L_{cm}\\ ## now if the body precessing around z axis and spinning about its own axis then angular velocity of body in lab...

Homework Statement [/B] I'm going exercises and I understand that if the circuit is short circuited that R=10 ohm is 0. (Trying to find Thevelin R in all of these btw) But then I ran across this one where when it's short circuited, isc is found using the current divider principle and it's...

I'm currently writing a paper over an experiment I did for class and I have a very stupid question over I need clarification on before I continue. I am using excel to graph out data, and I have determined that the error in my Length is .001 m. However, I am graphing the inverse of length to...

Homework Statement I'm asked to find the P (T < ?? ) , v= 26 , α = 0.005 2. Homework Equations The Attempt at a Solution From the table , we could notice that P (T > 2.779) , v= 26 , α = 0.005 , So , i think the ans should be P (T < -2.779 ) , v= 26 , α = 0.005 , But the ans is P (T <...

Hi! I have a problem understanding what happens when a plane electromagnetic wave hits a surface consisting of two medias of different optical density. My old school litterature tells me two formulas which I really don't understand where they come from. The same teacher starts by telling me...

I have been trying to fully grasp the concept of the Cauchy stress tensor and so I thought I'd make a post where I clear up my confusion. There may be subsequent replies as I pose more questions. I am specifically confused at how the stress tensor relates to the control volume in the image...

In rovibrational transitions we have following selection rules $$ \Delta v = \pm 1 $$ $$ \Delta J = \pm 1 $$ where ##v## is the vibrational quantum number and ##J## is rotational quantum number. Now based on whether ##\Delta J## changes to +1 or -1 we have two branches of spectroscopic lines...

Hi, I'm a little confused about the theory behind this problem related to fluids/Bernoulli's equation: "An airplane wing is designed so that the speed of the air across the top of the wing is 251 m/s when the speed of the air below the wing is 225 m/s. The density of the air is 1.29 kg/m3...

I was reading this wikipedia article: https://en.wikipedia.org/wiki/Ant_on_a_rubber_rope In the analytic solution section, it says that, at time ##t##, a point at ##x=X##, i.e. initially at a distance ##X## from the starting fixed point on a uniformly expanding rope moves with a speed...

Am I thinking about this problem correctly? "A block is attached to a horizontal spring and oscillates back and forth on a frictionless horizontal surface at a frequency of 3 Hz. The amplitude of the motion is 5.08 x 10-2 m. At the point where the block has its maximum speed, it suddenly splits...

Homework Statement Hi all, I'm having quite a big problem trying to understand the concept of enthalpy and free energy. I feel that a good way to sort this out is to write out what I understand about these things and have people correct me. Thanks in advance for any assistance. I'm learning...

I am confused about the units used in Kepler's 3rd law. Is T supposed to be in years or days? Is R supposed to be in kilometers or meters? Is there ever an instance where one combination of units is preferable over another (for example, if you want to use the answers from Kepler's third law to...

I've always struggled with circuits and never got a firm handle (hence the very basic questions...please bear with me). What I understand of Lenard's Experiment: Light hits the emitter plate and some electrons fly off. ...lol yeah that's about it. Here is one major confusion that I have: Not...

Hello everybody, Dirac notation uses "bras"( <a| ) and "kets"( |b> ), which are row vectors and column vectors respectively, but what would something like |a, b> mean? It makes no notational sense to me Context: A couple of photons going through beam splitters in an interferometer. One is...

Homework Statement Hi guy I am having a real issue trying to find the fundamental charge from my data. So here is the background. Basically I carried out and experiment where we measured an oil droplet the was floating a specific voltage by taking the measurement of 12 oil droplets and...

Homework Statement A two-stage rocket is traveling at 4500 m/s before the stages separate. The 3000-kg first stage is pushed away from the second stage with an explosive charge, after which the first stage continues to travel in the same direction at a speed of 3000 m/s . How fast is the...

So I have this problem I'm stuck on wrapping my head around a particular problem "In the sequence a{n}, let a{0}=2. If a{n+1} = 3 a{n} −1, then what is the value of a3?" I understand it's following the pattern of each term, and that with Arithmetic sequence a{n-1} means you would use the a{n}...

I have a discussion going on with some friends. The discussion goes like this: We have two identical tanks. One is empty. One is full of water. Both placed on the ground. They are connected with a hose at the bottom. There is a ball valve in line with the hose. The full tank has a given...

Homework Statement The figure shows Atwood's machine, in which two containers are connected by a cord (of negligible mass) passing over a frictionless pulley (also of negligible mass). At time t = 0 container 1 has mass 1.3 kg and container 2 has mass 2.7 kg, but container 1 is losing mass...

Homework Statement It's given that the total probability of event b =P(B) If A1 , A2 ... An are mutually exclusive and exhaustive events , then probability of B = Homework EquationsThe Attempt at a Solution P(B) = P(A1) x P(B | A1) + P(A2) x P(B | A2) + P(A3) x P(B | A3) + ... P(An) x...

Suppose I have a body of mass M kept on a horizontal smooth surface. I strike that particle with some force ,providing an impulse J_1. The applied force is in vertically downward direction. Suppose that the body deforms in this process and it doesn't rebound. What I want to know is, whether the...

Homework Statement I am confused between these 2 videos . In the first videos , it's same as what i learned in pre-university education course . When we are calculating kth percentile , the value that we get is whole number , then we need to the use (the value of the current number + value...

Homework Statement Hi, Alright so I have some confusion on when to use specific tests and the z vs t test. Given this example (not my homework) could someone please clarify. Alright say you have a random sample of size 200. You find the sample mean to be 10 and the sample standard deviation...

Homework Statement (see my attached photo to better understand where I am coming from!) So after some research, I've discovered that the current at different points in a simple series circuit is supposed to be the same value, and that the voltage is supposed to be different values. I...

Hi guys! (see my attached photo to better understand where I am coming from!) So after some research, I've discovered that the current at different points in a simple series circuit is supposed to be the same value, and that the voltage is supposed to be different values. I performed a lab on...

Homework Statement Uploaded question(the formula in c part) And can you tell me in which all cases that formula is used. Homework Equations Just want to know where the formula in c part has come from. The Attempt at a Solution Sum of magnetic fields due to circular plates calculated and added...

Homework Statement consider the rectangular bar undeformed a=b=2cm and c=20cm . The elastic modulus of the bar material is E=100 Gpa and its poissons ratio is u=0.3. The bar is subjected to biaxial forces in the x and y directions such that Fx=Fy=0.4x106 N and that Fx is tensile while Fy is...

I have a decent understanding of Nano and AMO physics, however when I started looking at colleges(applications started recently). I found out that the nano major is an interdisciplinary major or a specialization under either applied physics or electrical engineering. AMO is in some places its...

I'm trying to derive the Klein Gordon equation from the Lagrangian: $$ \mathcal{L} = \frac{1}{2}(\partial_{\mu} \phi)^2 - \frac{1}{2}m^2 \phi^2$$ $$\partial_{\mu}\Bigg(\frac{\partial \mathcal{L}}{\partial (\partial_{\mu} \phi)}\Bigg) = \partial_{t}\Bigg(\frac{\partial \mathcal{L}}{\partial...

This link shows us how to derive Hamilton's generalised principle starting from D'Alembert's principle. While I had no trouble understanding the derivation I am stuck on this particular step. I can't justify why ## \frac{d}{dt} \delta r_i = \delta [\frac{d}{dt}r_i] ##. This is because if I...