This is derivation 2 from chapter 8 of Goldstein:

It has been previously noted that the total time derivative of a function of ## q_i## and ## t ## can be added to the Lagrangian without changing the equations of motion. What...

adding time derivative to Lagrangian effect on Hamiltonian]]>

What is the fastest time can go?]]>

Q. Prove that If (x1,y1) and (x2,y2) are the coordinates of the two vertices of an Equilateral Triangle then the coordinates of the 3rd vertex (X,Y) are

$$X=\frac{x1+x2\pm\ √3(y1-y2)}{2},$$

$$Y=\frac{y1+y2\pm\ √3(x1-x2)}{2},$$...

Find the third coordinate of a vertex of an equilateral triangle]]>

Prove the integral of x*arcsine(x) from 1/2 to 1 is bounded between pi/16 and 3*pi/16

Not sure what to bound with. Do we use Squeeze Theorem?]]>

Then Simple question here : Sun is cool or hot??]]>

Estimating a mean from games of ruin]]>

Why doesn't the plate interact with the particle in double slit?]]>

I've been really curious about how TFP (Thin Flim Polarizer) works. I've searched TFP information through the Internet which tells that TFP utilizes Brewster's angle. This explains how the P-polarization transmits TFP with 100 % transmission, but I don't know how the S-polarization is...

How TFP (Thin Flim Polarizer) works?]]>

In the Standford case, some of the...

Psychology: The Stanford Prison Experiment was a Fraud]]>

from dBW to Watts = 10^(dBW/10)

This then gives RMS power in Watts

At what point do I convert this from a RMS to a peak...

Convert Power to a Peak Voltage, when to multiply by sqrt(2)]]>

So, as expected, my data looks like a ramp...

Smoothing Numerical Differentiation Noise]]>

This is an investigation I have been studying recently, can someone help with the following...

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

Method:

1. Place a toy car at the top of a ramp.

2. Let it go.

3. Measure the distance it travels from the bottom of the...

Stopping distance of a car rolling down a hill]]>

I literally just revised a website template and tried uploading it to 000webhost.com (free website hosting) today, but it didnt come out right. There was supposed to be a bunch of pictures and animations, but it came out as just text with a white background. Is there a solution to this to...

000webhost website upload didnt come out right]]>

The CDF from the characteristic function]]>

Trying to calculate an integral]]>

Can anyone help me provide basic ideas of solving these kind...

Equivalent capacitance]]>

Gravitational time dilation - acceleration vs potential]]>

What are non-inertial frames of reference?]]>

Force required to stop a given torque]]>

Solving the Basel problem using Gauss's law]]>

From the start, I think the earth/ground reference should be removed with a small isolating transformer. Do commercial units have...

Making a safe and effective fly zapper]]>

Help creating a coordinate system for a robotic arm]]>

I have no ability to perform anything more than addition, subtraction, multiplication or division. Yet, since my teenage years I have been fascinated, enthralled and intrigued by the skies. Astronomy and cosmology have been a decades-long interests of mine. I've read Hawking's 'A...

Is there any way forward for me?]]>

AA batteries in parallel]]>

Does the rocket exhaust exert a outward pressure on the nozzle walls due to the sheer volume of the exhaust gases or is the pressure a negative one due to the exhaust stream...

Pressure on the Walls of a Rocket Motor Bell Nozzle]]>

How to Better Define Information in Physics

View attachment 227134

...

How to Better Define Information in Physics - Comments]]>

Any thoughts on whether ENIG or bare copper would be...

Best PCB pad finish for repeated solder jobs?]]>

Schwarzschild from Minkowski?]]>

So I would think that gravity would be stronger from an approaching object that from a...

"Doppler" Gravity]]>

Too early to panic about having no plan post-graduation?]]>

So I'm trying to self-study AP Physics C and found the first volume of Halliday/Resnick's Fundamentals of Physics on my parent's shelf, 3rd edition (from 1988). They also have the 2nd edition of University Physics, volume 2 (E&M). I do, however, have a copy online of the extended 10th...

Difference Between 3rd and 10th Editions of Halliday/Resnick?]]>

I have a single air inlet that's being used as a cooling stream. It is channelled by a duct (or ducts, there are a few available designs) onto a piece of work...

Distributing airflow evenly]]>

A polymer chain consist of a large number N>>1 segments of length d each. The temperature of the system is T. The segments can freely rotate relative to each other. A force f is applied at the ends of the chain. Find the mean...

Polymer Chain in Statistical Mechanics]]>

I am passionate about Physics, Computer Science, and Aerospace Engineering. I am about to start my freshman year of college in the fall and have yet to decide which would be the most...

Should I major in Computer Science, Physics, or Aerospace Engineering?]]>

I am a new one to the world of the LED lights. However, I have an oncoming project with LED strips. There will be 3 separate runs of a LED strip (4 meters, 4 meters and 6 meters each). In each run LED strip will be put in 1 meter long LED strip profile. I am planning to connect the...

Powering an LED strip from a car battery?]]>

I don't see how they can increase torque AT ALL without having something stationary somewhere against which to apply force.. I can only see them as a fluid...

Torque convertors]]>

I made an experiment where I measured the change of the impedance of a coil when I changed a environment parameter X times.

For each change I collected ~20 samples.

So I have a table with X lines that represent the number the change of the parameter and 20 columns that represent the...

2 samples T test in case of non-normal distribution]]>

Making glass filaments]]>

Your photo must show a scene in bright sunshine. The photo must also be taken in bright sunshine (i.e. you can't snap a photo of the outside from inside a room).

1. Any digital photo or...

PF Photo Contest - If You Steal My Sunshine (6/16-6/23)]]>

In most problems involving projections I'm given a vector and the equation of a line either in parametric form or in symmetric form (ie. parametric: <0t+3, -t-4. 3t+2> or symmetric form: x=3, (y+4)/-1, (z-2)/3). However, when...

Difference between two vectors]]>

is it correct ? i am not...

Is it correct to calculate the number of particles]]>

I am thinking to use a password manager, but I am not sure 1) if it will help me remember my passwords, and 2) if it is secure.

If they are useful and secure, what are the best (free and commercial) password managers out there to use?

Thanks]]>

https://projecteuler.net/problem=58

Code (Python):

def prime(N):

if N == 1:

return False

y = int(N**0.5)

for i in range(2,y+1):...

if N == 1:

return False

y = int(N**0.5)

for i in range(2,y+1):...

View attachment 227124

View attachment 227125

This is an example given in the book . But I am just wondering whether the question itself is correct...

Is this question on Intensity of light from Sun correct?]]>

Is it that way because publishing cartographers came mostly from the northern hemisphere? Is there some reason related to navigation (like Polaris being over the north pole) that might motivate even a southern...

History question -- The choice of the North Pole being up or down]]>

Imagine there exists reference two frames, a frame O which is stationary and another, O' moving relative to O. If there is a four vector A--> (A

Vectors and frames question]]>

Brain–computer interfaces?]]>

My wife just drew this

View attachment 93241]]>

To protect against a nuclear EMP (NEMP) usually a big metal box is used, which is electrically connected to earth, to discharge the electrical pulse.

Most houses in europe have a 3-grid electric system, L, Neutral (N) and Protective...

Nanosecond Max Current of Residual-Current Circuit Breaker]]>

Usually, the clarinet is presented as acting like a pipe system closed at one end, which only allows for harmonics that are odd multiples of the fundamental frequency. I used the app "SpectrumView" by OxfordWaveResearch to measure the following spectrum:

View attachment 227118

Fair...

Frequency spectrum of a clarinet]]>

P.S. I prefer...

Suggestions for 9th Grade Physics Textbooks?]]>

Here is the problem.

Exercise statement: The switch have been closed for a long time y is opened at t=0. Using Laplace's transtormation calculate V0(t) for t ≥ 0

View attachment 227113

This is what i made to solve it:

1) I...

RLC circuit solved with Laplace transformation]]>

there was an article in the Stanford encyclopedia about QM that was rewritten.

it quoted a "multiprocess" interpretation differing from Everett's one which could be related to Bohm's interpretation. it is no more there.

i am wondering if there are interpretatins where different results...

Multiple processes interpretation]]>

Is I an observable?]]>

If ##x\sqrt{1+y} + y\sqrt{1+x } = 0##, then prove that ##\frac {dy} {dx} = \frac {-1}{(x-1)^2}##.

$$ \frac {dy} {dx} =

- \frac {\left (\frac {\partial f}{\partial x} \right)} {\left(...

Implicit differentiation problem]]>

Help with understanding a Friedmann flat universe]]>

It's official, Mechanics is hard!]]>

Two bachelor of science degrees, or a master’s degree?]]>

It's the first "limb pit" from a Civil War battlefield to be excavated, and experts say it opens a new window on what is often overlooked in...

Civil War Battlefield 'Limb Pit' Reveals Combat Surgeon Work]]>

A filament in a light bulb uses a length of wire 6.0cm. The potential difference across the filament is 240V. What is the force on an electron in the filament from the imposed electric field?

F=...

Force on an Electron]]>

Find the period of a low earth orbiting satellite using Kepler Laws

earth radius = 6.38E6 meters

T^2/R^3 for earth = 2.97E-19 (sec^2/m^3)

2.97E-19 = T^2/(6.38E6)^3

T^2 = (2.97E-19)(6.38^6)^3 =...

Calculating the period of a low Earth satelite using Kepler]]>

All of the references I cite are from Wikipedia.

Ex 1. Does the following isolated system have a calculable value for its entropy?

Assume a spherical...

Some confusion re entropy]]>

access to two copies of a web page, but _independently_ , i.e., to be able to move one copy

up while moving the other down. The standard options are using a splitter ( for desktops)

or an HDMI...

Viewing same Image/Picture Independently]]>

Thanks in advance!]]>

How to use Real Array Index in Matrix dimension?]]>

This was interesting. I recall it being very humid too!]]>

What is the fan curve for such a combination?]]>

Sudden reversal in a simple 3-phase motor's direction]]>

How to state the laws of refraction and apply them to....]]>

I am a physics hobbyist so generally the first answers should come with the least mathematics...

Do electromagnetic waves have potential and kinetic energy]]>

Looking For Research Experience in the future]]>

How does the ear distinguish multiple different pitches?]]>

Real life example of the energy contained at E=γmc^2]]>

Path integrals (and generalizations) are sums over configurations. A logical extension of that process would be to sum not over configurations, but over theories (configurations are possible solutions of a single theory).

Renormalization already plays around...

Summing not over configurations, but over theories]]>

Magnitude-5.3 earthquake hits Japan's Fukushima

http://www.usatoday.com/story/news/world/2013/09/19/japan-fukushima-nuclear-plant/2835493/

Wouldn't this violate the conservation of momentum?

p = E/c. That means on the way out, the momentum of light would be zero, but on the way back it...

Does infinite one-way speed of light violate p conservation?]]>

How to concentrate white light in a very small point?]]>

Is information lost in wavefunction collapse?]]>

P.S.: Not interested in string...

Regge theory and QCD]]>

How do the components of the stress-energy tensor act on gravity regarding

a) the FRW-universe?

b) a solid ball?

In a FRW-universe ##\rho + 3P## determines the second derivative of the scale factor. So, there are no non-diagonal components. Just theoretically,...

How does the stress-energy tensor act on gravity?]]>

The question states:

Speed of the Electron]]>

http://arxiv.org/abs/1805.00233

Hisham Sati, Urs Schreiber

(Submitted on 1 May 2018)

By analyzing super-torsion and brane super-cocycles, we derive a...

New perspectives on M-theory]]>

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

This question is from book Afken Weber, Mathematics for Physicist.

An operator ##T(t + ε,t)## describes the change in the wave function from t...

Proving the following properties]]>

If you go to have an X-ray, in the film there will be information detailing the dosage you just received. However I encountered a rather unusual one like this:

70kV 100mAs 100mS -- dGycm

What is the unit of measurement in this X-Ray?]]>

A vertical spring has one end attached to the ceiling and a 3kg bag attached to the other one. When the system is at rest, the spring is stretched by 40cm. 1) determine the spring constant. 2) Let the bag drop from a position in which the spring is not deformed....

Spring Conservation of Energy]]>

"A loan of 10,000 is repaid by twenty level installments at the end of every six months. The nominal interest rate is 8%, convertible half-yearly. Find the total amount of interest payment made over the ten-year period."

How to calculate total interest from annuity-immediate?]]>

https://medium.com/@philipkd/special-relativity-explained-with-a-deck-of-cards-f99bfd873bd5...

Request for Feedback on Special Relativity article]]>

Is -OH used both -I effect and +I effect? When used it -I effect and +I effect?

Is -OH used both -I effect and +I effect? When used it -I effect and +I effect?

-OH when used as -I effect and +I effect?]]>