Daily Habits for improving Physics/Math Knowledge and skill]]>

if i sharpen 2 pencils with 2 different Diameters (thin and jumbo), which one will have a higher torque ( while sharpening), thus make it harder to sharpen?

Let's assume that the angle of the pencil tips are the same, both have same wood of same density, the push force is the same...

Torque for sharpening pencils with different diameters]]>

STEVE Phenomena]]>

How can I model a density function of a compressible fluid?]]>

A DC current is flowing between two electrodes through a iron disk medium. Positive is attached to the copper shaft of the disc and the negative is attached to the outer brass periphery of the disk. The radius of the disk is...

Need help with the magnetic field generated by this current distribution]]>

ABC is a triangle

The angle A = 30 degrees

AB = 7cm

BC = 5 cm

C is an acute angle. Find the size of angle C?

I need to use the cosine rule here Cos C = (a^2 + b^2 - c^2) / 2ac

Cosine rule]]>

I must do a report on Chernobyl: before, during and after.

I have all I need except for a clear and simple explanation of how steam explosions work in this regard.

All the online sites I've been on provide information that is too advanced, and as a non native English speaker, the...

Chernobyl and steam explosions]]>

(The equation was obtained by Dimensional Analysis)

here x and t are both...

The order of calculating velocity and position alters the solution?]]>

Problem Statement

Given bivariate normal distribution ##X,Y \sim N(\mu_x=\mu_y=0, \sigma_x=\sigma_y=1, \rho=0.5)##,

determine ##P(0 < X+Y < 6)##.

My Approach

I reason that

$$ P(0 < X+Y < 6) = P(-X < Y < 6-X)$$

$$ =...

Calculating Bivariate Normal Probabilities]]>

I want to make or buy a device that when installed on a piece of rental equipment a person can push a button and it sends a signal back to my office and...

Need a little advice -- How can my customers report rental equipment that needs service?]]>

Question about SETI]]>

Basically, I use a portable electric space heater to keep my room warm during the winter, and it works quite well, except it makes a very loud hum that keeps me awake, so my options right now are poor sleep due to hum or having my room drop to about 12 C over night if I turn the heater...

Converting a household space heater to DC]]>

Can a defective DRC on a heat pump cause the fan motor to go bad?]]>

How is momentum conserved if you lose kinetic energy?]]>

Plate Tectonics: Origins and Implications]]>

I am making a prototype and I need an electromagnet with a wavelength of the order of centimeters. The magnetic field can be 10 mT or more.

Microwave have magnetron in it, but they don't...

UHF/SHF Electromagnet]]>

Assuming you know the core mass, and other data about the sun, such as temperatures and pressures. Find the density at the very center of a star.

I think this may be involved.

P(r) =...

Calculate the density at the centre of the Sun]]>

"In a given sample of mesons, half will decay in 18 nanoseconds (18 x 10

Time Dilation Problem with Mesons]]>

Consider a turbine which actuates the windmills by blowing air into it. (If we use beat steady windmills (which is called reverse windmills) instead of movable windmills, deliberate the following conditions by parametric view....

Question about a Windmill / Turbine]]>

In a GFCI receptacle we have in most of our homes. The sense coil can output zero when there is deviation from net magnetic field between the line and neutral. This means the cancellation...

What happens when magnetic fields cancel]]>

Photon detector on a dual slit experiment]]>

Here is the last page of part 5.

https://www.physicsforums.com/threads/random-thoughts-part-5.851969/page-134]]>

It's about 0.4" (10mm) long. I guess these are moth cocoons. The insect left them behind and looked like flying moths.

How many kind of moths are there, and how does insecticide exactly get rid of them? Does it work on their lungs or the blood stream? Just...

Moth Cocoon Insecticide]]>

What causes SWR to change along a feed line?]]>

Monitoring calls from Z.exe to foo() in Y.sys, a driver]]>

Playing trombone to 'wildlife':

]]>

referencing this paper by Baily & Loeb @ Harvard Smithsonian Center for Astrophysics

Oumuamua may be an alien lightsail?]]>

The given distance element is

$$ ds^2 = e^{2 \lambda} dt^2 -...

Finding the Ricci tensor for the Schwarzschild metric]]>

Charge of the vacuum]]>

Namely, do any of them overlap with one another? To give an example,

A counterfactual statement can be something like "A possible world where I won the lottery."...

Predicate logic and modal logic]]>

Unusual bug]]>

Do you use Mathematica/Maple to help you with problems?]]>

In Griffiths (2nd edition) pgs 110-111 - deriving the uncertainty principle

I have 2 questions

1)

I am stuck on a point ...

(h = ^ hat )

<f | g > = < ( Ah - <A>) ψ | ( Bh - <B>) ψ >

= <Ψ | ( Ah - <A>) ( Bh - <B>) Ψ>

FOIL

= <ψ | AhBh ψ> - <B><ψ | Ah ψ> - <A>< ψ | Bh ψ> +...

The Uncertainty Principle - question within Griffiths' Text]]>

Seeking a derivation of Schrödinger's wave equation]]>

Consider an electron in a hydrogen atom in the presence of a constant magnetic field ##B##, which we take to be parallel to the ##z##-axis. Without the magnetic field and ignoring the spin-orbit coupling, the eigenfunctions are...

Spin-orbit coupling and Zeemann effect]]>

MathType - best font for equations?]]>

Very recently however, Peter Shor and Lee Smolin had a discussion about this over at...

Naturalness: dimensionless ratios]]>

I mean, glass is used to focus lasers so it's odd that lasers...

Lasers Versus a Psychic Force Bubble]]>

The circuit of FIGURE 2 shows a 10 kΩ potentiometer with a 5 kΩ load. Determine the position of the slider on the ‘pot’ when the voltage across points ‘XX' is 3 V.

Potentiometer electrical engineering question]]>

I've been looking at some power...

Harmonics in Power Systems]]>

A 1kg cart, a 0.1kg ball, and an elastic cord connecting the ball and the cart, are placed in a weightless environment; see Figure. The cart has the shape of a symmetric trapezoid with its left and right edges at a 60-deg angle...

Impulse and Momentum: Ball and cart connected by a cord]]>

Space Stuff and Launch Info]]>

My wife just drew this

View attachment 93241]]>

I've read that the formula is as follows (assuming wye termination):

Original Turns Per Tooth # * Original KV = New Turns Per Tooth * New KV

which can be rearranged:

(Original Turns...

BLDC Motor Re-Winding]]>

Charge carrier density, Hall experiment vs Fermi-Dirac statistics]]>

Updated about an hour ago

Fri 4 May 2018, 7:44pm

http://www.abc.net.au/news/2018-05-04/volcano-in-residential-area-in-hawaii/9728316

video on that page

lots of other links .......

Hawaii's Kilauea volcano eruption]]>

A snake with a mass equals to m is placed on a scale. The length of the snake is L. Suddenly the snake starts moving with a constant velocity v

Finding F using F=dP/dt]]>

The equation of motions of a series of pendulums coupled by a torsion spring is this:

##\ddot{\Phi_i}=-\frac{k}{ml^2}(2\Phi_i-\Phi_{i-1}-\Phi_{i+1})##, where k is the torsion spring constant, m is the mass of a single pendulum,...

Static solutions of a series of coupled pendulums]]>

a source of sound of frequency f emits sound with speed v, is at rest. If an observer is moving at towards source with speed u, then wavelength of sound waves observed by the observer will be?

f' =...

Apparent wavelength in Doppler's effect]]>

Problem:

a continuous beam ABC simply presses, loaded with a distributed load q, the length of the beam is 2L.

EI=constant

View attachment 235883

find the reactions in the beam ,we use Castigiliano method.

Castigiliano method]]>

I have been going through Griffiths’ Intro To Quantum Mechanics in an attempt to self-teach myself some quantum mechanics.

I am currently in section 3.4 (Generalized Statistical Interpretation)

I am seeing a “step” occur more than once. When I first came across it, while I didn’t...

Griffiths' Intro to Quantum Mechanics - primed variables]]>

How is fuel pumped in fighter aircrafts? (F-16 etc.)]]>

Hi

I am looking at this proof that , if on an open connected set, U,there exists a convergent sequence of on this open set, and f(z_n) is zero for any such n, for a holomorphic function, then f(z) is identically zero...

Complex function open set, sequence, identically zero, proof]]>

A ball A is rotating on a table with an angular velocity ω about its vertical axis. An identical ball B collides with the ball A elastically. After collision the ball A starts sliding over the table. The coefficient of friction...

Collision with a ball spinning about its vertical axis]]>

lets say we have a electric motor with 1kw at 1500 rpm and that is 4.75 N.m

when the electric motor is connected to worm gearbox n proportion 10:1 then the speed on output point of the gearbox will be 150 RPM. But this mean...

Question about forces in a gearbox]]>

This is one of our yearly theme. It's the time of the year, so show us your favorite photo of a Christmas tree, all decorated for the season.

1. Any digital photo or digitally-scanned photo relevant to the...

PF Photo Contest - O' Chrismas Tree (12/15-12/21)]]>

A twin "paradox" in General Relativity]]>

Humor Award]]>

Chaos Theory Constants]]>

Parallel Universes: Multiverse vs Many Worlds - Splits?]]>

So, What I am aiming for is a roughly cylindrical vessel (it can, and I think probably has to, be tapered to achieve the effect) with the air being pumped out of one end, and a...

Pressure differences in a leaking vacuum vessel]]>

I am bewildered by so many different notions of probability distribution percentages, i.e. the proportion of values that lie within certain standard deviations from the mean.

(1) There is a Chebyshev's inequality:

- for any distribution with finite variance, the proportion of the...

Chebyshev inequality, confidence intervals, etc]]>

Simple method for testing graphene]]>

= 116 kg/km

So a a bit over metric ton gets you up to 10 km altitude. 2 metric tons at a 30 degree angle. Still gives you 25,000 pounds potential drag without breaking the rope.

Working strength is...

Feasibility of stratopheric wind turbines?]]>

Wigner's Friend

View attachment 234008

Continue reading the Original Blog Post.]]>

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

The boundary between two different materials can be divided into two different kind of phases: bulk phases and surface phases. For example, let's...

Surface tension in terms of temperature and concentration of an added substance]]>

I just learned that velocities don't purely add: 2m/s + 2m/s does not equal 4m/s, but something like 3.9999999...9 m/s, and so on. Something to do with the upper limit of c.

Logic makes me assume that this...

Understanding the Relative Velocity Paradox]]>

As many know, when an external force acts on a rigid body and the force's line of action does not pass through the body's center of mass ##c.m.##, the force will cause the body to both translate and

Body rotating about its center of mass]]>

A point charge (q) is located a distance (b) from a grounded conducting sphere with radius (a) show that the...

Induced charge distribution]]>

There are planty...

What has changed since the Copenhagen interpretation?]]>

I have a...

3D Equillibrium Statics Problem - Reaction Forces/Moments]]>

What happened? Lack...

Current State of Nuclear Fusion Power]]>

All I (as a physicist) really Need to Know ...]]>

CLIC is a proposed accelerator, potentially at CERN, that would collide electrons and positrons at energies far above what previous colliders achieved. Its overall energy would...

CLIC proposal]]>

Help on REU statement please]]>

Math Challenge - November 2018]]>

Now suppose that A and B always show both a 1 or both a 0. This would be a strong correlation between A and B.

Now could this be called 'a coincidence'? And if...

Can this be called 'a coincidence'?]]>

Sub-atomic particles

The Copenhagen Interpretation

Black Holes

Bubble universes and the Multiverse

Many Worlds Theory

The Holographic Proposal

Quantum entanglement

Causality, determinism and free will]]>

Suppose that all stars in this galaxy were born in a single major-merger burst event about 10

Gyr ago. From this original burst, I want to compute the fraction of stellar mass still surviving as stars...

From the original burst, fraction of stellar mass still on the Main Sequence]]>

Note that I really don't know anything about quantum anything, but I'm trying to do some reading up on "randomness" and the consensus seems to be that this,...

Is radioactive decay truly random?]]>

If the length of the filament of a heater is reduced by 10%, the power of the heater:

Options are-

a) increases by about 9%.

b) increases by about 11%.

c) increases by about 19%.

d) decreases by about 10%.

Electric Power - Which formula to use and when?]]>

My name is Joseph I am a physics student, I am new to Fortran, I know how to write a code for solving differential equations, but now I have a physics equation for evolving star rotation as a function of mass. and I do not know how to evolve (using any numerical method, such as Euler) so...

Physical time (years) in simulations]]>

The most common isotopes can receive one or two neutrons being stable, but if a neutron would be...

Why there is a general lack of neutrons in the Earth?]]>

I am a high school student and currently studying Mechanical properties of fluid.

We are taught surface tension in a very introductory level and most of it is about liquid-gas surface tension.

We are taught that liquid-vapour tension is the atrractive forces that...

Explaination of Solid-Liquid and Solid-gas surface tension]]>

View attachment 235802

View attachment 235803

View attachment 235804

View attachment 235805

Dave]]>

Before SSB:

Electroweak - U(1) symmetry on fermion spinors and Higgs complex doublet, 1 conserved current

Electroweak - SU(2)...

Clarification about conserved currents in the Standard Model]]>

I want to take apart a comcast remote. Even after I take the batteries out, there are no screws under the battery cover like on older remotes to take them apart.

View attachment 235897 - Super small seam here around the remote is...

Taking apart a remote, is there a special tool?]]>

I am Yanna and I am building a racing car. I am now trying to calculate the tire drag of this car when cornering, but I'm stuck on something.

In order to find the tire drag, I need the normal load on each wheel. To find this, I made some equations:

1) the sum of the normal load...

Normal load on the tires of car]]>

Einstein's elevator]]>

RIP PF Member Morbius]]>

Will this buy us a...

Maunder Minimum & Climate Change]]>

I want to simulate the Circular Restricted Three Body Problem in excel, however I don't know how to get started, even though I have the equations of motion.

The Planar, Circular Restricted Three Body Problem assumes that one body, m3, is neglebtaly small, and the two other bodies move...

Simulating the Three Body Problem]]>

I wonder how to see if the distribution is normal or not based on the numbers in the table. I attach the screenshot with the table, and it is written that "the distribution appears to be bimodal", so it appears to have two peaks. I understand the the question sounds silly, but I truly...

Define if the distribution is normal or not]]>