Physics Forums | Science Articles, Homework Help, Discussion

Wrong value for voltage across capacitor

invalid@example.com (AfterSunShine) — Sun, 14 Oct 2018 02:06:44 +0000

1. The problem statement, all variables and given/known data
The current through a 100 microfarad is i(t) = 50 sin(120*pi*t) mA
Calculate the voltage across it at t = 1 ms. Consider zero initial voltage.
2. Relevant equations
v(t) = (1/c) integral of i(t) from t = 0 to t = t

3....

Wrong value for voltage across capacitor

Wireless communications system

invalid@example.com (JJgo) — Sun, 14 Oct 2018 02:05:54 +0000

1. The problem statement, all variables and given/known data
A wireless communications system can achieve a theoretical maximum data rate of 200 Mbps using 16-QAM modulation in a 10 MHz channel and using a single spatial stream. What data rate could theoretically be achieved if the same...

Wireless communications system

Show that a continuously differentiable function is not 1-1

invalid@example.com (Eclair_de_XII) — Sun, 14 Oct 2018 02:05:47 +0000

1. The problem statement, all variables and given/known data
"Let ##f:ℝ^2\rightarrow ℝ## be a continuously differentiable function. Show that ##f## is not one-to-one."

2. Relevant equations
A function ##f:ℝ^n\rightarrow ℝ^m## is continuously differentiable if all the...

Show that a continuously differentiable function is not 1-1

Differentiation with units- Related Rates problem

invalid@example.com (opus) — Sun, 14 Oct 2018 02:04:11 +0000

1. The problem statement, all variables and given/known data
A spherical balloon is being filled with air at a constant rate of ##2cm^3/sec##.
How fast is the radius increasing when the radius is 3 cm?

2. Relevant equations

3. The attempt at a solution
This is a problem...

Differentiation with units- Related Rates problem

How does a digital ammeter work?

invalid@example.com (fourthindiana) — Sun, 14 Oct 2018 01:53:04 +0000

I am a student at a trade school, majoring in HVAC. My electricity for HVAC textbook has a chapter on electric meters. However, my textbook does a poor job of explaining how a digital ammeter works.

My textbook has the following description of how digital ammeters work: "To make meters...

How does a digital ammeter work?

Conditions for the applicability of u-substitution

invalid@example.com (justthisonequestion) — Sun, 14 Oct 2018 01:36:22 +0000

What are the conditions for applicability of u-substitution, i.e. when does it not work? Note that I'm not asking when is it a bad idea (that won't get you any closer to evaluating the integral), but are there any conditions that cause u-sub to yield wrong answers?

I started running into...

Conditions for the applicability of u-substitution

Is Simultaneity still alive in QM?

invalid@example.com (referframe) — Sun, 14 Oct 2018 01:35:03 +0000

In Classical Mechanics, according to SR, the concept of simultaneity is dead, a meaningless concept. But in QM, entanglement implies that some limited form of simultaneity exists. If we have two particles correlated due to entanglement, a measurement of one particle immediately...

Is Simultaneity still alive in QM?

Oscillating horizontal mass attached to a spring with Friction

invalid@example.com (Miguel Orta) — Sun, 14 Oct 2018 01:22:48 +0000

1. The problem statement, all variables and given/known data
The question is similar to last week’s, except that we will consider how friction may damp the oscillation with time. A block with mass m shown in the drawing is acted on by a spring with spring constant k. The block is pulled...

Oscillating horizontal mass attached to a spring with Friction

Doubt regarding Lorentz contraction

invalid@example.com (Kaguro) — Sun, 14 Oct 2018 01:19:14 +0000

Hello all.

I am having some small trouble with applying the lorentz transformations to calculate lorentz contraction. Here's what I did:

Let O be the rest system and O' be the system moving with velocity v w.r.t O along x axis. Consider a rod lying in the O' system with ends x1' and x2'....

Doubt regarding Lorentz contraction

Can I use Microsoft Visual Studio For coding C ?

invalid@example.com (Arman777) — Sun, 14 Oct 2018 01:06:59 +0000

I will take Intro to C programming this semester and can I use MVS for coding C ?

How can we feed 20 billion people

invalid@example.com (wolram) — Sun, 14 Oct 2018 01:01:12 +0000

It is reported that there will be 20 billion people by the year 2050, just how are we to feed them unless drastic changes are made to farming and food wastage.

https://www.sciencedaily.com/releases/2018/10/181010132300.htm

Modified Newtonian dynamics

invalid@example.com (Elbraido) — Sun, 14 Oct 2018 00:57:04 +0000

Hello Everbody
In Sci Shows newest video they take about alternates to Dark Matter and one of these is Modified Newtonian dynamicse. The guy states that there were two teams one proved that it existed and the other did the the opposite.
My question is why they can't and didn't...

Modified Newtonian dynamics

Finding the kernel of an action

invalid@example.com (Mr Davis 97) — Sun, 14 Oct 2018 00:40:36 +0000

1. The problem statement, all variables and given/known data
Let ##\mathbb{F}_3## denote the field with 3 elements and let ##V = \mathbb{F}_3^2##. Let ##\alpha, \beta, \gamma, \delta## be the four one-dimensional subspaces of ##V## spanned by ##(1,0), (0,1), (1,1)## and ##(1,-1)##...

Finding the kernel of an action

Understanding Yield Strength & Stress Strain Curve

invalid@example.com (tomtomtom1) — Sun, 14 Oct 2018 00:39:54 +0000

Hi all

I was hoping someone could shed some light on the following:-

I am trying to understand what Yield strength is and understand the exact limit of where elastic and plastic deformation occurs on a stress strain curve.

Correct me if I am wrong but I define:-

Yield strength as the...

Understanding Yield Strength & Stress Strain Curve

Attempting to prove each theorem in a book

invalid@example.com (Terrell) — Sun, 14 Oct 2018 00:32:10 +0000

I am seeking advice on how to effectively and efficiently learn mathematics textbooks. Currently, I adopt the style of trying to prove theorems in the book before reading the provided proof. I have had good success in this; I noticed a considerable gap in experience between me and my peers in...

Attempting to prove each theorem in a book

Help With Understanding Hooke's Law

invalid@example.com (tomtomtom1) — Sun, 14 Oct 2018 00:21:10 +0000

Hi all

I was hoping someone could help me understand Hookes Law.

Hooke’s Law, states that Stress is proportional to Strain.

The bit I am struggling to understand is that Stress is F/A and Strain is Change in Length/Original Length, so if Stress is proportional to Strain then shouldn't...

Help With Understanding Hooke's Law

What's wrong with my if-else statements in python 3?

invalid@example.com (astroman707) — Sun, 14 Oct 2018 00:17:36 +0000

Goal:
I'm trying to allow the user to input varying spellings for certain auto services, and still have my code work properly. My goal was to use the if-else statements to ensure that if the user misspelled a service, the code could correct the error by changing the variable assignment to the...

What's wrong with my if-else statements in python 3?

Confused about units

invalid@example.com (JesseK) — Sun, 14 Oct 2018 00:02:57 +0000

1. The problem statement, all variables and given/known data

I've an equation here: h = 3270 Pa / 1,0 g/cm^3 × 9,81 m/s^2 = 33 cm

How did those units cancel out to make it cm? That's something I don't get.

2. Relevant equations

Given above.

3. The attempt at a...

Confused about units

Green's functions issue

invalid@example.com (joshmccraney) — Sun, 14 Oct 2018 00:00:25 +0000

Hi PF!

The ODE $$g''(x) + (1-k^2)g(x) = f(x)\\ g(0) = y(\pi/3) = 0$$
where ##f(x)## is a forcing function and ##k \in \mathbb N## is a constant has a Green's function via variation of parameters as
$$
G_L = \frac{L(y)R(x)}{W} : 0 G_R = \frac{L(x)R(y)}{W} : 0 $$

with...

Green's functions issue

Why isn't tungsten used in nuclear reactors?

invalid@example.com (Mackenzie Cobb) — Sat, 13 Oct 2018 23:48:08 +0000

Me again, with another potentially ignorant nuclear science question:

Why isn't tungsten used to prevent meltdown in nuclear reactors?

If tungsten has a higher melting point of tungsten is almost 6200 degrees Fahrenheit, and nuclear meltdown happens when the uranium fuel is some 5200 degrees,...

Why isn't tungsten used in nuclear reactors?

Momentum of a System and External Forces

invalid@example.com (gibberingmouther) — Sat, 13 Oct 2018 23:27:17 +0000

So Pearson is telling me that, basically, the ratio of internal to external forces and the briefness of the time interval is what determines whether the external forces on a system whose momentum we're studying will affect whether we can obtain a decent approximation of the momenta of the...

Momentum of a System and External Forces

Redox titration

invalid@example.com (Kolika28) — Sat, 13 Oct 2018 23:23:12 +0000

Cl2(g) + 2I–(aq) -->I2(aq) + 2Cl–(aq) (reaction 1)
[2S2O3^(2-)(aq) + I2(aq) --> S4O6(2-)(aq) + 2I–(aq) (reaction 2)

Why isn't n(I2)(reaction 2)=2n(S2O3^(2-))(reaction 2). I don't see why this is wrong.

Magnetic field inside a solenoid calculated with Ampere's law

invalid@example.com (Limddong) — Sat, 13 Oct 2018 23:08:53 +0000

I think the real magenetic field is sum of the magnetic fields calculated in each cross section of solenoid with various angle and same center axis when i apply Ampere's law. (Imagine the cross section contains a part of center line of the solenoid) Please let me know why we don't do like that. :)

Radioactivity level in the coolant water

invalid@example.com (oksuz_) — Sat, 13 Oct 2018 22:55:07 +0000

Hi,

Can anyone give me a source from which I can obtain the radioactivity level in the coolant water circulating in the primary circuit?

Thanks in advance.

GCC warning: function may return address of local variable

invalid@example.com (m4r35n357) — Sat, 13 Oct 2018 22:46:54 +0000

Yes I've already looked on SO! None of the answers contain the word "may". My story is that I am passing in references to global variables, modifying them, and returning them in array literals. I suppose it must complaining about the array literals (c99) rather than the variables themselves,...

GCC warning: function may return address of local variable

Fourier Transform integral

invalid@example.com (Martin89) — Sat, 13 Oct 2018 22:40:16 +0000

Hi All! I've been looking at this Fourier Transform integral and I've realised that I'm not sure how to integrate the exponential term to infinity. I would expect the result to be infinity but that wouldn't give me a very useful function. So I've taken it to be zero but I have no idea if you can...

Fourier Transform integral

Stabilization of H2O2

invalid@example.com (doctoxin) — Sat, 13 Oct 2018 22:35:40 +0000

I happened to come to this site by chance. I was checking solubilities of a few compounds I am considering mixing and came across a thread where people were discussing sodium percarbonate and hydrogen peroxide. Someone mentioned about stabilization of the H2O2 but no one could remember what...

Stabilization of H2O2

Hello everyone

invalid@example.com (lotusdraconis) — Sat, 13 Oct 2018 21:58:46 +0000

im currently studying in high school and taking AP Physics classes. I really wanna improve my physics and will probably be an engineer.

I need a book to solve Schrodinger's eqn numerically

invalid@example.com (jonjacson) — Sat, 13 Oct 2018 21:56:55 +0000

I have found this one that looks perfect:

https://www.amazon.com/Computationa...6827702&sr=8-6&keywords=schrodinger+numerical

THe problem is that it has not been published yet :( , but I can't believe...

I need a book to solve Schrodinger's eqn numerically

Volume of Parametrised Surface

invalid@example.com (Tom31415926535) — Sat, 13 Oct 2018 21:55:34 +0000

1. The problem statement, all variables and given/known data
Let C be the parametrised surface given by

Φ(t,θ)=(cosθ/cosht, sinθ/cosht,t−tanht), for 0≤t and 0≤θ<2π

Let V be the region in R³ between the plane z = 0 and the surface C.

Compute the volume of the region V ....

Volume of Parametrised Surface

Artificial gravity in a rotating space station

invalid@example.com (substitute materials) — Sat, 13 Oct 2018 21:27:15 +0000

It is often proposed that gravity could be simulated on a space station by rotating around an axis, such that the astronaut experiences the centripetal force of the space station wall, analogously to gravity. It is usually mentioned that the radius of rotation must be very large to avoid...

Artificial gravity in a rotating space station

How do I become better at understanding Physics?

invalid@example.com (lawlieto) — Sat, 13 Oct 2018 21:21:29 +0000

This will be a semi-rant about my miseries at life but mostly I'm looking for some useful advice. If you read this and write some useful comments I'll be very grateful. Guys, I'm so desperate to be better at physics but I feel like I keep failing. My story: I did A levels in the UK (it's like...

How do I become better at understanding Physics?

All current 'hints' towards Dark matter not being "matter"

invalid@example.com (AlenKovac) — Sat, 13 Oct 2018 21:15:04 +0000

I want to start by saying that I'm in no way trying to say that Dark Matter isn't a real pehonomenon in space. I also have no intention to sway one way or another. However, I feel like most scientiests are swaying towards the 'dark matter' is some kind of WIMP or such. It's much easier to read...

All current 'hints' towards Dark matter not being "matter"

How to show that commutative matrices form a group?

invalid@example.com (Robin04) — Sat, 13 Oct 2018 20:53:48 +0000

Let's say we have a given matrix ##G##. I want to find a set of ##M## matrices so that ##MG = GM## and prove that this is a group. How can I approach this problem?

Calculate the expectation value of V from Ehrenfest's theorem

invalid@example.com (Faizan Samad) — Sat, 13 Oct 2018 20:46:57 +0000

1. The problem statement, all variables and given/known data
I have a general question how I calculate the expectation value of V (potential energy) with Ehrenfest’s theorem. Do I have to integrate d

/dt with respect to d. Also if the potential is symmetric (even) would that mean the...

Calculate the expectation value of V from Ehrenfest's theorem

Roulette Prediction Algorithm Problem

invalid@example.com (shlomi123) — Sat, 13 Oct 2018 20:42:27 +0000

The roulette prediction algorithm is described here: http://pingless.co.il/roulette.pdf

And I have a problem with the formula attached
View attachment 232112
Where teta θ is position, velocity and acceleration of the ball. g is garvity force. r is the ball radius from...

Roulette Prediction Algorithm Problem

Numerical approximation of area under curve

invalid@example.com (Taylor_1989) — Sat, 13 Oct 2018 20:25:50 +0000

I am very new too Matlab and how it all works but I am having trouble understanding at what axis the numerical integration is occurring from on the graph that I plotted.

So I am currently doing an experiment in gamma ray spectroscopy and due to issue with the software we found it hard to...

Numerical approximation of area under curve

Doctoxin - who am I

invalid@example.com (doctoxin) — Sat, 13 Oct 2018 20:17:40 +0000

I taught at a university for 10 years and during that time I was also a reservist in the military. When 9/11 happened I was activated and remained on active duty for 15+ years as a specialist in chemical and biological warfare agents. I worked mostly in toxicology. I deployed to Afghanistan...

Doctoxin - who am I

Fraunhofer's multiple slits versus atomic scatteres (diffraction theory)

invalid@example.com (Gamdschiee) — Sat, 13 Oct 2018 20:11:23 +0000

Hey, I am currently busy with studying solid state physics and looking at diffraction theory. Following link explains Frauenhofer diffraction pretty good: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/mulslid.html#c3

Let's assume a N=6 multiple slits. Its diffraction pattern...

Fraunhofer's multiple slits versus atomic scatteres (diffraction theory)

Deriving Lorentz Transformation

invalid@example.com (Arman777) — Sat, 13 Oct 2018 20:02:53 +0000

How can we derive Lorentz Transformation ?

I used one approach using the length contraction and time dilation and simultaneity but my prof wasnt much happy about it. Is there any other way to derive it ?

International Physics Studies Program (IPSP) University of Leipzig program review?

invalid@example.com (sid0123) — Sat, 13 Oct 2018 19:40:51 +0000

Hello everyone,
My name is Sid and I am about to finish my engineering degree in Mechanical Engineering. Hopefully, I will be graduating with an Upper Second Honors. I am interested to study Physics now, specifically Theoretical HEP. I have decided to apply to IPSP (Internatioanl Physics...

International Physics Studies Program (IPSP) University of Leipzig program review?

How to make a simple x vs y graph in Google docs

invalid@example.com (sp3sp2sp) — Sat, 13 Oct 2018 19:20:47 +0000

If I select two columns of data what are the steps to make a simple x vs y graph of that data? I know its sort of a dumb question but i cant see how to do this. It automatically suggests any graph other than a basic x vs y. Thanks for any help

Finding Force by using the coefficient of friction and mass

invalid@example.com (Alejandro Nava) — Sat, 13 Oct 2018 19:18:22 +0000

1. The problem statement, all variables and given/known data
A man pushes a 50 kg box up a 20-degree ramp at constant velocity. If the pushing force is parallel to the ramp, and the coefficient of friction is 0.4, how much force is he pushing with?

2. Relevant equations
u=Fs,...

Finding Force by using the coefficient of friction and mass

Does the EPR experiment imply QM is incomplete?

invalid@example.com (kurt101) — Sat, 13 Oct 2018 18:55:43 +0000

I know this has been discussed in so many ways on this forum, but it is hard for me to separate interpretations, fact, speculation, and inaccuracies. You can probably just skip the next two paragraphs that I describe the EPR/Aspect experiment and go right to my question.

In an EPR experiment...

Does the EPR experiment imply QM is incomplete?

Show that given conditions, element is in center of group G

invalid@example.com (Mr Davis 97) — Sat, 13 Oct 2018 18:54:36 +0000

1. The problem statement, all variables and given/known data
Let ##G## be a finite group and ##m## a positive integer which is relatively prime to ##|G|##. If ##b\in G## and ##a^mb=ba^m## for all ##a\in G##, show that ##b## is in the center of ##G##.

2. Relevant equations

3....

Show that given conditions, element is in center of group G

Schwarzschild singularity and black hole

invalid@example.com (jeremyfiennes) — Sat, 13 Oct 2018 18:52:30 +0000

Are a Schwarzschild singularity and a black hole the same thing?

Tension in a string being pulled from both ends

invalid@example.com (AAAA) — Sat, 13 Oct 2018 18:42:24 +0000

1. The problem statement, all variables and given/known data
If you have a string being pulled on each end by 60N, what is the total tension in the string?

2. Relevant equations
N/A

3. The attempt at a solution
The answer in my textbook says 60N, but it doesn't make a...

Tension in a string being pulled from both ends

Artificial gravity in a spacecraft

invalid@example.com (Halit) — Sat, 13 Oct 2018 18:42:16 +0000

1. The problem statement, all variables and given/known data

https://i.hizliresim.com/Bzp05M.jpg "spacecraft"

View attachment 232147

Now you're in other space.No gravity at all.You 're going to make your own artifical gravity R = 100m
Quest
1-) With which...

Artificial gravity in a spacecraft

Statistical Mechanics- moments/cumulants, log expansion

invalid@example.com (binbagsss) — Sat, 13 Oct 2018 18:27:35 +0000

1. The problem statement, all variables and given/known data

Using log taylor expansion to express cumulants in terms of moments

I have worked through the expansion- ##log(1+\epsilon)= ...## see thumbnail- and that's ok; my question is why does the expansion hold, i.e. all i can see is...

Statistical Mechanics- moments/cumulants, log expansion

Central-Force Motion Problem

invalid@example.com (sams) — Sat, 13 Oct 2018 18:23:26 +0000

In Chapter 8: Central-Force Motion, in the Classical Dynamics of Particles and Systems book by Thornton and Marion, Fifth Edition, page 323, Problem 8-5, we are asked to show that the two particles will collide after a time ##\tau/4√2##.

I don't have any problems with the derivations and with...

Central-Force Motion Problem

Compare the speed and frequency of a wave in a thick rope

invalid@example.com (YMMMA) — Sat, 13 Oct 2018 18:22:35 +0000

1. The problem statement, all variables and given/known data
In the attached file.

2. Relevant equations
No equations needed.

3. The attempt at a solution
I answered it B. Not sure,though. If it is a thick rope the frequency decreses; therefore, the speed decreases.

Gauss' Theorem

invalid@example.com (sams) — Sat, 13 Oct 2018 18:21:58 +0000

In Mathematical Methods for Physicists, Sixth Edition, Page 60, Section 1.11, the Gauss' theorem is written as:
View attachment 231423
In Mathematical Methods for Physicists, Fifth Edition, Page 61, Section 1.11, the Gauss' theorem is written as:
View attachment 231424
Kindly I would...

Gauss' Theorem

Power line EMI filter + feedthrough filter for a Faraday cage

invalid@example.com (flowwolf) — Sat, 13 Oct 2018 18:15:34 +0000

Dear forumers,

I need a 50hz 250VAC power line filter for an EMI shielding faraday cage. The filter should work between 100khz and 20ghz, attenuation should be >=60dB between 1mhz - 5ghz.

Regular power line EMI filters like this
View attachment 231363
don't seem to go that high (only...

Power line EMI filter + feedthrough filter for a Faraday cage

General Irreducible Representation of Lorentz Group

invalid@example.com (CharlieCW) — Sat, 13 Oct 2018 18:01:46 +0000

This one may seem a bit long but essentially the problem reduces to some matrix calculations. You may skip the background if you're familiar with Lorentz representations.

1. The problem statement, all variables and given/known data

A Lorentz transformation can be represented by the...

General Irreducible Representation of Lorentz Group

Could someone review and help me on a link i wrote on SR

invalid@example.com (arydberg) — Sat, 13 Oct 2018 17:52:20 +0000

I would like for someone to review and help me on a link i wrote on SR. Is this possible?

Link:
http://www.maverickexperiments.com/SpecialRelativity/SpecialRelativity2.html

Al

Effect of errors due to branching and acceptances

invalid@example.com (CAF123) — Sat, 13 Oct 2018 17:45:47 +0000

Say I have say 10 measurements of an experimental observable e.g differential cross section with respect to rapidity , one measurement in each bin and corresponding statistical and systematic uncertainties given in % per bin.

Now, suppose I want the value of this dsigma/dy after correcting for...

Effect of errors due to branching and acceptances

Assignment of 2D array

invalid@example.com (davidfur) — Sat, 13 Oct 2018 17:26:53 +0000

Hi guys,
On with my Fortran adventures...I'm trying to accomplish a simple task: assign a 2D array with some reals. Here's an excerpt from the code:

Code (Fortran):

subroutine get_energy_and_grad(natoms_,coords,ereal,gradmat)

include 'cbka.blk'
include 'opt.blk'
integer, intent(in)...

Assignment of 2D array

Favorite songs (new thread)

invalid@example.com (DennisN) — Sat, 13 Oct 2018 17:01:07 +0000

I was looking for the previous "Best songs ever" thread, but it seems it is gone. So I boldly start a new one...

The very talented 21 year old Norwegian singer and songwriter Sigrid:

...

Favorite songs (new thread)

Can you fire Elon Musk as CEO?

invalid@example.com (nsaspook) — Sat, 13 Oct 2018 16:49:45 +0000

I'm pretty sure a company like Tesla could crater without him as the intellectual explorer and inspiration but 60% of TSLA's ownership is Institutional Investors. I would not be happy with the stock today....

Can you fire Elon Musk as CEO?

A New Interpretation of Dr. Walter Lewin's Paradox - Comments

invalid@example.com (rude man) — Sat, 13 Oct 2018 16:43:29 +0000

Greg Bernhardt submitted a new PF Insights post

A New Interpretation of Dr. Walter Lewin's Paradox
View attachment 227296

...

A New Interpretation of Dr. Walter Lewin's Paradox - Comments

Black holes squishing Earth

invalid@example.com (DaveC426913) — Sat, 13 Oct 2018 16:30:54 +0000

This may be condensed matter physics topic, but I'm looking for a layperson answer.

Scares of the CERN accelerator creating a black hole that swallows Earth are in the news once again.
https://www.newsweek.com/earth-shrunk-tiny-hyperdense-sphere-particle-accelerators-1145940
From 10...

Black holes squishing Earth

How beneficial is a minor in Electrical Engineering?

invalid@example.com (QCDsoup) — Sat, 13 Oct 2018 16:28:09 +0000

Hi, I’m a freshman Physics major in the US and I am concerned about the job opportunities directly out of undergrad. Because of this, short of switching my major to an engineering field, I was wondering if a minor in EE would substantially assist me. I know it would not be an ABET accredited...

How beneficial is a minor in Electrical Engineering?

Different answers for division in python 3

invalid@example.com (issacnewton) — Sat, 13 Oct 2018 16:24:32 +0000

Hello

Consider the following code in Python3

Code (Text):

n = 226553150
m = 1023473145
n*m = 231871064940156750
int(n*m/5) = 46374212988031352
n*m//5 = 46374212988031350

Now since ##n*m## is divisible by ##5##, both should be give the same answer. But the first is wrong and second is...

Different answers for division in python 3

Applying pressure for clearing land mines

invalid@example.com (ferchotous) — Sat, 13 Oct 2018 16:08:21 +0000

Hi, Im a Industrial Design student working on my senior Thesis. Since antipersonal landmine cleareance is a very dangerous process; im working on a remote controlled vehicle concept that will be able to do a controlled detonation. That way the human wont have to manually disarm the landmine...

Applying pressure for clearing land mines

Momentum in special relativity

invalid@example.com (exponent137) — Sat, 13 Oct 2018 16:07:08 +0000

Although I thought that I understand special relativity enough, I cannot now clearly answer on the following question:

What is the most direct derivation, why momentum in special relativity is ##p=\gamma m v##, where ##v## is velocity of the rocket? Let us assume that Lorentz equations are...

Momentum in special relativity

Career in "Reactor Physics and Core Design"

invalid@example.com (Syed Alam) — Sat, 13 Oct 2018 15:49:25 +0000

Dear all,

I have completed my MSc and PhD in Nuclear Engineering (Reactor Physics and Core Design) from a UK university. I am currently working at a National Lab in France.

Can you please suggest/recommend me a site where I can find the most suitable jobs related to Nuclear...

Career in "Reactor Physics and Core Design"

Statics and equilibrium - asking for some guidance

invalid@example.com (Finn J) — Sat, 13 Oct 2018 15:22:57 +0000

Hi,

I'm not used to communicate physics in English, so my language may be a bit off.

This task is fairly simplistic. It's a figure which is held up in points A and B (both having an x and y force exerted on them), and the figure has a joint C. It is depicted in attached files.

The answers...

Statics and equilibrium - asking for some guidance

Phase angle and Phase in Simple harmonic motion

invalid@example.com (Yoseph Santoso) — Sat, 13 Oct 2018 15:10:46 +0000

I'm a teacher at a Senior High School in Indonesia. I have two Senior High School physics books (Indonesian book) written about simple harmonic motion formula:

y = A sin θ = A sin (ωt + θ₀) = A sin 2πφ = A sin 2π (t/T + θ₀/2π)
phase angle = θ = ωt + θ₀...

Phase angle and Phase in Simple harmonic motion

What is a good axial piston pump for this application

invalid@example.com (ENGBIO) — Sat, 13 Oct 2018 15:05:39 +0000

So I posted yesterday about appropriate pumps for pumping water out of a ballast tank in a manned submersibles at a depth of 1000m. I decided to switch to an axial piston pump. I got that the require pump head is approx. 410 m and the required power input provided by the pump is approx. 18 000W....

What is a good axial piston pump for this application

Russian style nuclear powered drive for a space ship?

invalid@example.com (consuli) — Sat, 13 Oct 2018 14:59:46 +0000

Russia has developed a micronized nuclear powered drive for ballistic misiles and cruize misiles. This is obviously a very aggressive and environment polluting...

Russian style nuclear powered drive for a space ship?

Text limit - character count - in a post?

invalid@example.com (jim mcnamara) — Sat, 13 Oct 2018 14:53:27 +0000

https://www.physicsforums.com/threads/the-short-story-thread-post-yours-here.914630

@Drakkith has a nice thread about writing stories. He mentions a limit to the number of characters in a post.
What is that value? I think vBulletin used to have a setting for...

Text limit - character count - in a post?

Magnetization relation to magnetic field applied

invalid@example.com (igurman) — Sat, 13 Oct 2018 14:52:18 +0000

A few simple questions which I am not sure about, it's about NMR.

First sentence: "A magentic field B0 is applied on a sample, If the applied magnetic field B0 is stronger, the magnetisation of material is greater" . Would you say that sentence is correct? As I understood, magnetization is a...

Magnetization relation to magnetic field applied

Cannon on a vertical tower

invalid@example.com (jasonchiang97) — Sat, 13 Oct 2018 14:37:58 +0000

1. The problem statement, all variables and given/known data

A cannon that is capable of firing a shell at speed v₀ is mounted on a vertical tower of height h that overlooks a level plain below.

Show that the elevation angle α at which the cannon must be set to achieve...

Cannon on a vertical tower

Verify that this kinetic energy operator is Hermitian

invalid@example.com (sa1988) — Sat, 13 Oct 2018 14:28:42 +0000

1. The problem statement, all variables and given/known data

Not actually a homework question but is an exercise in my lecture notes.

2. Relevant equations

I'm following this which demonstrates that the momentum operator is Hermitian:

View attachment 191320

3. The...

Verify that this kinetic energy operator is Hermitian

Pilot-wave is No More, Pilot-wave cracked by Bohr

invalid@example.com (jedishrfu) — Sat, 13 Oct 2018 13:14:32 +0000

Pilot wave Quantum Mechanics is doomed from recent experiments but wait there's more:

https://www.quantamagazine.org/famo...ve-alternative-to-quantum-weirdness-20181011/

Pilot-wave is No More, Pilot-wave cracked by Bohr

Refraction of a wave

invalid@example.com (jha192001) — Sat, 13 Oct 2018 13:10:59 +0000

(1)What is the real cause of refraction?
Light wave cannot possible have a change of speed in going onto diffrent medium hence what is going on inside actually that we say its a change of speed.
(2) I am notable to comprehend how a change in wavelength not always means a change in frequency. If...

Refraction of a wave

Velocity through spacetime

invalid@example.com (runningc) — Sat, 13 Oct 2018 13:10:47 +0000

I have read that the velocity of a body through spacetime is equal to 'c'.
Can I therefore draw a spacetime velocity diagram (triangle) with sides: "v" velocity through space....

Velocity through spacetime

Gradient and direction

invalid@example.com (Mathematicsresear) — Sat, 13 Oct 2018 13:08:43 +0000

1. The problem statement, all variables and given/known data
Is the gradient perpendicular to all surfaces or just level surfaces?
For instance, if I I have a function f(x,y)=z where z is the dependent variable then...

Gradient and direction

Best anode materials for water-based hydrogen generator?

invalid@example.com (sauroman1) — Sat, 13 Oct 2018 13:01:28 +0000

I want also to build electrolysis based hydrogen generator or and water oxygenator/aerator. It's simple electrolysis device but requires special electrodes that are corrosion resistant or at least safe for human consumption. I seen that hydrogen bottles use platinum titanium electrodes. Platinum...

Best anode materials for water-based hydrogen generator?

PF Photo Contest - Autumn (10/13-10/19)

invalid@example.com (ZapperZ) — Sat, 13 Oct 2018 12:40:11 +0000

Autumn

Autumn is in full swing in the northern hemisphere. So this week, our theme is on this season of the year. Your photo must clearly show the flora and fauna of the season.

Contest Rules:

1. Any digital photo or digitally-scanned photo...

PF Photo Contest - Autumn (10/13-10/19)

VOTE PF Photo Contest - Slooooooowww

invalid@example.com (ZapperZ) — Sat, 13 Oct 2018 12:36:48 +0000

Last week, our theme was on things that move very, very, slowly. So please vote for the photo that best represents our theme.

1. kuruman
View attachment 232141

2. epenguin
View attachment 232142

3. morrobay
View attachment 232143

4. ZapperZ
View attachment 232144 ...

VOTE PF Photo Contest - Slooooooowww

Is the ground state energy of a quantum field actually zero?

invalid@example.com (jcap) — Sat, 13 Oct 2018 12:30:58 +0000

I start by outlining the little I know about the basics of quantum field theory.

The simplest relativistic field theory is described by the Klein-Gordon equation of motion for a scalar field ##\large \phi(\vec{x},t)##:
$$\large \frac{\partial^2\phi}{\partial t^2}-\nabla^2\phi+m^2\phi=0.$$
We...

Is the ground state energy of a quantum field actually zero?

Superposition - is the theory valid?

invalid@example.com (Svenns) — Sat, 13 Oct 2018 11:56:07 +0000

Hello
My friend claims that the theory of electron superposition has been overturned recently. That this was due to measurement errors, and that electrons fly like orbs and planets in orbits, but I can not find any sources.
I am asking for an answer, thank you very much.
(I'm sorry, I have no...

Superposition - is the theory valid?

Lorentz invariance and equation of motion for a scalar field

invalid@example.com (eoghan) — Sat, 13 Oct 2018 11:43:20 +0000

Hi there,

I just saw some lectures where they claim that the Klein Gordon equation is the lowest order equation which is Lorentz invariant for a scalar field.
But I could easily come up with a Lorentz invariant equation that is first order, e.g.
$$
(M^\mu\partial_\mu + m^2)\phi=0
$$
where M is...

Lorentz invariance and equation of motion for a scalar field

A variation of the twin paradox

invalid@example.com (imsmooth) — Sat, 13 Oct 2018 11:37:44 +0000

I've read the twin paradox and if I am correct the resolution is that one twin accelerates and decelerates so he comes back younger. But I have a different scenario that I would like to ask:

What if you have two twins equally distant from a point in space and completely at rest relative to each...

A variation of the twin paradox

What sparked your interest for physics?

invalid@example.com (Bobman) — Sat, 13 Oct 2018 11:10:57 +0000

For me it was something as trivial as a conceptual example of newtons third law, the astronaut creating momentum by tossing a wrench, that gave me an eyeopener for the subject.

What ignited your spark?

Distance to 3rd and 5th nearest ion to S2- in ZnS structure

invalid@example.com (Vishesh Jain) — Sat, 13 Oct 2018 10:49:10 +0000

Hey folks

ZnS has a ccp structure with S2- ions forming FCC lattice with Zn2+ ions at half the tetrahedral voids

View attachment 232138

Attached is a table showing no. of nearest neighbours and their distance for an S2- ion

'a' is edge length of the unit cell

I want to know how the...

Distance to 3rd and 5th nearest ion to S2- in ZnS structure

Synchronous induction motor

invalid@example.com (zsolt2) — Sat, 13 Oct 2018 10:33:18 +0000

1. The problem statement, all variables and given/known data
A star-connected, three-phase synchronous induction motor takes a current of 10 amps from a 415 volt supply at unity power factor when supplying a steady load. If the synchronous reactance is 5 ohms/phase and the resistance is...

Synchronous induction motor

Regarding the measurement of horsepower

invalid@example.com (thetexan) — Sat, 13 Oct 2018 10:14:07 +0000

I teach aerodynamics. One horsepower is 550 lbs moved one foot in one second.

My question is this. Does that assume that the 550 lbs is being lifted vertically against gravity? As opposed to moving, say, a 550 lb chunk of concrete across a floor.

And if so, does the gravity value of...

Regarding the measurement of horsepower

Soyuz launch failure with crew on board (crew is fine)

invalid@example.com (mfb) — Sat, 13 Oct 2018 09:00:25 +0000

A Soyuz flight that was supposed to launch two astronauts to the ISS had a booster failure (half an hour before this post). The Soyuz capsule separated from the rocket and landed, the crew is fine. Rescue teams got to them quickly. While they had to endure higher g-forces than usual they...

Soyuz launch failure with crew on board (crew is fine)

Probability theory: Understanding some steps

invalid@example.com (WWCY) — Sat, 13 Oct 2018 08:35:25 +0000

1. The problem statement, all variables and given/known data
Hi all, I have some difficulty understanding the following problem, help is greatly appreciated!

Let ##U_1, U_2, U_3## be independent random variables uniform on ##[0,1]##. Find the probability that the roots of the quadratic...

Probability theory: Understanding some steps

Superconductors and Wiring

invalid@example.com (kiki_danc) — Sat, 13 Oct 2018 08:33:49 +0000

Zero resistance in wiring seems to be the technology in the future. Any resistance in the transmission wiring acts like loads so it's like the current wastes itself on the resistances in the wiring and heat that occurs. So lossless wiring seems to be the ultimate goal.

In Large Hadron Collider,...

Superconductors and Wiring

Momentum of a stationary particle/wave?

invalid@example.com (Philip Land) — Sat, 13 Oct 2018 07:29:23 +0000

We are all familiar with Heisenbergs uncertainty principle. When we determine the position of a particle or wave, the uncertainty of momentum reach infinity.

So lets say I have a machine that measures the position very very precisely. Then the uncertainty of this non-moving particles momentum...

Momentum of a stationary particle/wave?

Determine the Transition Wavelength

invalid@example.com (Samuel Williams) — Sat, 13 Oct 2018 07:25:14 +0000

Hi all, the question is as follows:

1. The problem statement, all variables and given/known data

From the energy level diagram for OH in the study guide, it can be seen that the first rotationally
excited level of OH (²∏₃₌₂ J =5\2) lies 120 K above the...

Determine the Transition Wavelength

High frequency circuits

invalid@example.com (mertcan) — Sat, 13 Oct 2018 07:17:55 +0000

Hi, initially I have seen that when circuits are exposed to high frequency kirchoff laws become invalid. According to my search I can not find any derived circuit equations for that case, instead computational electromagnetism method is suggested using maxwell. Is it the only way to make...

High frequency circuits

Structure of Matter in Quantum Field Theory

invalid@example.com (DarMM) — Sat, 13 Oct 2018 07:00:51 +0000

This is a topic I've mentioned a few times before. Essentially the structure of matter in quantum gauge field theories is unclear to me. I have no clear question here, just some initial discussion points.

So at the first level, it seems a particle based view of quantum field theory is difficult...

Structure of Matter in Quantum Field Theory

Leading clocks lag, the twin paradox and the Doppler effect?

invalid@example.com (Sorcerer) — Sat, 13 Oct 2018 06:36:57 +0000

I have an obvious understanding failure here, so hopefully someone can help me clear this up. Thanks for reading this obnoxious drivel.

Leading clocks lag

So, if two clocks are fixed to a the ends of a barn, and they are set off with light pulses from the midpoint, in the frame of the...

Leading clocks lag, the twin paradox and the Doppler effect?

How useful would Chemistry be as a 2nd major to Physics

invalid@example.com (amys299) — Sat, 13 Oct 2018 06:28:39 +0000

So this upcoming fall I'm beginning college and decided to pursue a BS in Physics. Although I'm not exactly sure what field I want to pursue in physics, I think I want go into quantum mechanics after I graduate and obtain my PhD.

Although I love chemistry, it's not what I want to do as a career...

How useful would Chemistry be as a 2nd major to Physics

Interference Between Two Speakers -- Real Life Version of a HW problem

invalid@example.com (Albertgauss) — Sat, 13 Oct 2018 06:11:46 +0000

Hello,

Many of you are familiar with the homework problem that goes like the below, and though straightforward to solve in most general physics homework sets, I need to help getting it to work, which is not so easy in real-life.

Consider two speakers separated by 2.0 meters. Find the points...

Interference Between Two Speakers -- Real Life Version of a HW problem

Over-complicating physics concepts

invalid@example.com (starstruck_) — Sat, 13 Oct 2018 05:33:39 +0000

I’m not sure what’s up but I find myself over complicating concepts that are new and ones that I was really good with and have been practicing for the last like 3 years.

I find myself trying to connect things to previous concepts but it isn’t working out.

I’m in second year but I’ve found...

Over-complicating physics concepts