why a conductive shield doesn't block the magnetic field?]]>

Calculate maximum safe volume for headphones]]>

In principle the equation is well known.

(1)

But is there any experimental proof of this equation? I know...

Magnetic field of moving charges]]>

edit:

Ok, there was a misconception on my side that I want to clarify changing the original title by this one:

If there are two planets, rotating one around the other, and only gravity is acting. Is it...

Can a force generate rotation with moment arm=0 ?]]>

First time poster here so please excuse any mistakes as I'm unfamiliar with the conventions of this forum. Also before I get started I'd like to say I wasn't sure exactly where a question like this would go; I debated in the Math Programs and Latex section but figured general physics...

Understanding Fourier Transforms]]>

]]>

Calcuating retinal irradiance from the sun]]>

How quickly can an electric switch operate?]]>

In case A we have a magnet and a ball bearing just sitting on the table. We bring another ball bearing close to the magnet. The bearing is grabbed by the magnetic force.

In case B, we add another bearing, number 3 as shown. Now...

Where does the energy come from?]]>

If anyone can give me the answer, please keep it very simple - I was never any good at physics or higher math.

It's very easy and only requires a claw-hammer to do. Very low tech.

Hold the hammer at the end of the handle with the claw...

Where does the torque come from?]]>

I'm currently working on a project for which I need to measure the advancing contact angle of a liquid on a solid, specifically the advancing contact angle of a molten thermoplastic on carbon fibers.

My understanding is that there is a difference between dynamic contact angles...

Measuring advancing contact angle]]>

Were still in the calculation phase and I've made a list of concepts to consider:

Projectile motion ( ball to rim)

Air resistance ( is this negligible? )

Velocity of shooter at apex of...

Physics behind shooting a basketball.]]>

But how does elongating the time duration of a force reduce the noise?

Does it have something to do with the frequency of the vibration?

In the case of impact...

How does a floor mat dissipate noise/vibration?]]>

It says that what powers the circuit is actually current, does it mean that voltage and resistance variation is ok as...

Basic electronics Concepts. Can you please help me?]]>

What do we know about the formula for air drag force?]]>

This is the situation.

Work done to pull a spring is ½kx

The human lens is like a spring. Linear, and obeys Hooke’s law.

Work done to stretch the lens is also ½ kx

Legal to inverse an equation?]]>

Alright, so after looking at this video to do it

I did the following.

F1(65N) = 65cos(30)i+65sin30i

Then using the radian circle I saw that 30* has x,y coordinates of sqrt3/2 and 1/2 respectively. So as shown in...

Question about Resultant Forces]]>

Heat convection in liquid nitrogen]]>

Suppose we have a leader in a homogeneous magnetic field caused by two strong magnets (btw, which causes the strongest magnetic field?). Assume now that a charged ion travels through the magnetic field. It will mean a...

Induced voltage and current in an odd scenario]]>

I am reading a book on Fermat's principle and I don't understand one step in the mathematical derivation.

R is the radius of the circle.

C is the source of light that travels to I through two paths COI and CDI.

m is the inverse of...

Fermat and Snell again]]>

2D becomes 3D when looked at by one eye]]>

The Problem Statement

I have a jet entering leaving a nozzle at u

I am trying to equate the rate of momentum diffusement (or spread)...

Jet Spread Rate K Values- Momentum diffusement]]>

Where does the current go]]>

View attachment 107895

an electron comes flying in electric field between two capacitor plates. Let's say that voltage is 12V and distance between plates is 1m. Electric field E=U/d=12V/m. Plates are connected to the battery just initially. The battery is later...

Electron accelerated in electric field]]>

I have a 2-part question about electromagnetism and motors]]>

I...

Measuring charge (or potential) with electroscope?]]>

So I did an experiment.

we had radioactive material which was emitting beta particles, and we were using geiger counter to measure pulses (ionized beta particles). We were supposed to measure the time it takes for the geiger counter to...

Beta radiation and Alpha radiation]]>

First stop should be our very our PF Insights blog which hosts many physics tutorials...

Physics Learning Resources]]>

Kepler 3rd law for circular orbits]]>

forced vibration on mass between two pull springs]]>

Lightning Rod]]>

I just watched an ep of "Timeless", a new series about time travelling hijinks.

In this ep, they want back to the Nevada bomb tests of 1962 and stole a plutonium core of what looked like the Fat Man atomic bomb. They brazenly took the ~4 inch...

toxicity of Fat Man plutonium]]>

Storm Wind Force]]>

My question is that the manual says to use 2dcosΘ=mλ instead of 2dsinΘ=mλ( bragg diffraction...

Bragg diffraction]]>

My understanding thus far is that it is a traveling disturbance in the electric field. This picture here seems to help me see what is happening:...

Electromagnetic radiation effect on electric field?]]>

$$ \int

|\hat{P}(x)|^2 d^3x $$

I have been unable to find much information about this term. In their derivation of the Hamiltonian of...

What is the polarization energy?]]>

Lenz's Law in action with different length magnets]]>

I remember once reading in some science book by Isaac Asimov that the heaviest any flying animal can be is 22 kg, but I read on Wikipedia that Quetzalcoatlus may weighted up to 250 kg. So how come there's such a great difference in that...

How much could heaviest flying animal weight?]]>

In particular I want to built a RF Plasma cleaning chamber, however, I am not sure how to design the...

What is the approximate impedance of an RF plasma "antenna"?]]>

Dropping a Black Hole from Tower of Piza]]>

Where does kinetic energy go in inelastic collision?]]>

I assume that there are just two diffraction gratings that are rotated relative to each other, but could someone explain mathematically how to predict...

Two Diffraction Gratings - Rotation]]>

But how do we theoretically calculate the resistance of the bottom case? ( now, the current flow is not parrallel, current flows from bottom through the right side)

I would like to know if there is any references for this...

Resistance calculation on right angle current flow]]>

2. What is the relationship between air temperature, pressure, and air drag? I can see how on a warmer day the molecules are further...

Air friction and speed & temperature]]>

Need confirmation of planetary distances]]>

But my question is according to Gauss law, the electric field inside the conductor is zero. then how come this question says

"The electric field in a 2.5mm×2.5mm...

Electric field inside a conducting wire]]>

Thanks in advance for your answers]]>

i need a fresnel collimated UV light with adjustable focus. don't trust the ordinary lens because of optical aberration. one with a diameter of...

Where can i buy an ordinary optical collimator]]>

The problem statement

If I had a ball (balloon) filled with fluid at pressure P being acted on by two opposing forces F+ and F-

View attachment 107778

F+ being larger than F- there would be a net force accelerating...

Bernoullis & Pressure Gradient force]]>

So I started reading papers about the Lyapunov Exponent, but there is something I do not understand in the formula. Why...

Lyapunov Exponent]]>

Given the change in temperature and pressure is constant to find heat added to an mono-atomic ideal gas we use

Q=ΔU + W = 3/2 nRΔT + PΔV = 3/2 nRΔT + nRΔT

so Q=5/2 nRΔT correct?

But given the heat added to an ideal gas, constant pressure that...

Isobaric formula]]>

Why do some but not all derivatives have physical meaning?]]>

View attachment 107574

I have a particle being forced by a radial centripetal force onto a smaller radius

$$l_1=m_c.v_1.r_1$$

$$L_1=L_2$$

$$L_2=m_c.v_2.r_2$$

$$m_c.v_1.r_1=m_c.v_2.r_2$$

$$v_1.r_1=v_2.r_2$$...

Bathtub Vortex Pressure difference]]>

Out of interest, I've been perusing online about connections that exist between statistical physics and theoretical computer science. For example, consider the following report by Pietro...

Relations between statistical physics and theoretical CS]]>

]]>

Does a humam body movement generate a vacumm trail? and more]]>

A statistical definition of Young's Modulus?]]>

The information about the curvature on the rest]]>

[QUOTE="Charlie313, post:...

Non-reversibility of '2nd Law' processes]]>

Picturing this in my head on a number line, with just 3 photons at a time, and lets just say the wavelength is 1 and speed is 1, and at time t=0 we have a photon at...

Superimposing 2 sources of light slightly out of phase]]>

Charge Separation and solar cells?]]>

Is Fermat’s principle appicable to a plane wave?]]>

Entropy unavailable to do work]]>

Net force on 'ground' with object on top of it...?]]>

How would one use the conservation of angular momentum to explain the attached picture?

The rod is held fixed horizontally..the person holds on to the cork and then lets go...apparently the glass is saved due to this conservation...]]>

Mixing CO2 and N gasses.]]>

i need the help in understanding the following points:

1- In E&M, what is happening (physically) at anomalous absorption?, and how is this explained by the form of permittivity (real and imaginary parts)?

2- why did the "electric

I'd like to know which of these 3 example I sketched would have a steadier and higher air humidity at measuring point, assuming same conditions (except those illustrated as different, like porous media thickness and measuring point), water level and air turbulence within larger container...

Water wicking up porous media and air humidity ?]]>

Why are there only 6 colors?]]>

Hey guys, I want to ask a question about the Coulomb force or the electrostatic force.

As you can see, there are these statement,

1) The electric force is a "vector quantity"

2) The electric force between two stationary...

What is the *truth* of the electrostatic force]]>

Conservation of momentum sign]]>

So the initial acceleration, if someone...

Acceleration to reach space]]>

Why does Planck's BB emissive power increase with n?]]>

Conservation of Momentum with Friction?]]>

Can anyone explain this sun reflection in terms of angles?]]>

Imagine I'm watching a constant live feed from a camera on a space ship that's next to me, and this spaceship then takes off to Mars. When the spaceship reaches Mars, the video feed that...

noob question about time]]>

The answer is 1/sqrt(5) and I don't get why.]]>

When making calculations and solving problems, it is often nessecary to understand when forces are equal to zero, and when they are not. Since every force has an equal and opposite...

Confusion about Newton's laws, sum of forces equals zero]]>

I have a thought experiment which seems inconsistent with the 2nd Law of Thermodynamics, so there is probably a flaw in the idea somewhere.

Imagine a single molecule of a heavy gas (such as SF6) in a pipe 2.5 metres high and 100mm diametre. The pipe is upright and under the normal...

Thought Experiment on the Second Law of Thermodynamics]]>

1) mass m and speed v

2) 0.5 m and 2v

3)0.5m and sqrt 2 v

Simple math tells me the number 2 would require more energy to stop it. I can relate to energy better in terms of how to stop a moving mass...

To stop a moving object -- Momentum or Kinetic Energy]]>