I tried to open the top, but I couldn't - it wouldn't budge at all.

Then I shook the jar - so the sauce inside moved around.

I tried again and I effortless opened the jar.

Now - this got me thinking, why when I shook the jar did it open easily?

prior to...

Opening a top on a jar]]>

In physics, I've always been told that gravity is a force that ALWAYS works between "objects" with mass. Now, it seems clear to me that if a feather and a hammer were to be dropped at the same time on earth (without air...

Why do objects fall at the same speed in free fall?]]>

Divergence of downhill flowing water]]>

Eratosthenes angle measurement]]>

I'm investigating in using a dieletric barrier discharge for gas treatment, if I have two electrodes isolated by dieletric and the discharge gap between both of them has AIR..

how the ionization of air will take place, from where the source of electron which is going to start the...

Mechanism of discharge in DBD? (dieletric barrier discharge)]]>

Also I was wondering is it possible to make continuity...

Ion conductor question]]>

“Think of the wire as a horizontal cylinder. If you apply an electric field pointing to...

Why is the electric field in an ideal wire zero?]]>

In N side there are free electrons. In the positive charged side of the depletion region, there are...

A couple of questions about diodes and the depletion region]]>

1) Would current flow, and if so, what would the flow of electrons look like?

2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like...

Magnetic Field of an AA Battery 'Immersed' in a Conductor]]>

Copper and magnetism]]>

Fluid flow through a pipe constriction - what would you feel]]>

We also know that, our Sun's spectrum is blackbody like, while a...

How to approach a more perfect blackbody?]]>

Absolute zero temperature is impossible to achieve?]]>

- A body frame rotates with a body. It need not be aligned to the rotation axis.
- Angular momentum vector always aligned with rotation axis (not deviates from it).
- An observer on the body surface (body frame) observes no motion on a body....

Rigid Body Rotation]]>

Chief Ray Angle and Field of View]]>

Does black hole stop light or time?]]>

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...

Refraction formula confusion]]>

Fusion power, still the king of power?]]>

Stream inside paraffin oil when exposed to high volage]]>

An Integral Result from Parseval's Theorem

View attachment 207015

...

An Integral Result from Parseval's Theorem - Comments]]>

What is the electrostatic force field?]]>

But how do you visualize this? First we have a voltage at the beginning, and that causes current to flow. Then a...

Transmission line voltage delay]]>

I am reviewing some thermodynamics and heat engines. Heat engines are cyclical machines able to convert a portion (just a portion) of the thermal energy extracted from a hot reservoir into mechanical work. The residual thermal energy must dump into a lower temperature reservoir....

Heat engines can organize thermal energy]]>

Orbital mechanics is a bit of mystery to me.

Let us have a particle with mass

Particle spiraling into the Sun due to "drag" force?]]>

In this book I found by chance on Google, the author claims that “solutions of the wave equation only take the form of functions (...) in one and three dimensions. In two dimensions solutions are more complex”. Then, at the end of the paragraph of interest...

Is this book correct regarding waves in even dimensions?]]>

I've been pondering a problem with a current carrying wire in a magnetic field. The Lorentz force is easy, ILB,

with a velocity 90 degrees to the B field. So let the force accelerate the wire. Assume only one segment of the wire that has current in one direction, say up, is in the...

Dynamics of Lorentz force on a current carrying wire]]>

Question regarding centripetal force]]>

It says that the capacitors are in parallel, but why? I can´t understand this point, and it certainly seems as if they are...

Why are these capacitor in parallel?]]>

View attachment 215436

and

View attachment 215438

Can they both be called the general form?]]>

But, suppose the Earth were 10 times bigger.

Would it be possible for everything on Earth to scale with this increase - Earth systems, land masses, trees etc (but also remain unchanged to us (except everything everything would be bigger)....

Scale factor question]]>

Accelerating it from 0 to 1 m/s takes 0.5*1*1^2 - 0 joules, which is 0.5 joules.

But accelerating it from 10 to 11 m/s takes 0.5*1*11^2 - 0.5*1*10^2 joules, which is 10.5 joules.

This doesn't make much sense to me as the...

Why does it take more energy to accelerate faster objects?]]>

I have been doing an experiment at school looking into how the angle of a cone affects the time it takes for it to fall 2m. The data consistently shows an inverse relationship but it is unclear whether or not they are inversely proportional i.e. if the angle doubles, the time taken to fall...

Investigating Drag with Paper Cones]]>

View attachment 215250

This is the basic principle of an aeolipile.

You should be able to calculate the rotating velocity right? Knowing the mass and ignoring any resistance.

But then...

How to calculate rpm of an aeolipile]]>

Research paper

http://science.sciencemag.org/content/early/2017/11/01/science.aao5392]]>

On Antimatter]]>

If an ideal body of water is insulated and has a constant source of heating applied to it, can its temperature be expected to rise linearly?

(No. Even as I write this I see it

temp curve of heating water]]>

Car battery has no lead why]]>

And i have a dumb question about light.

When the diffraction is studied, we look at where the light is coming. But not where the light comes from.

When the gravitational deviation is studied, we look at where the light comes from, but not where the light comes.

What do you think?...

Diffraction and gravitational lensing]]>

What is a "Pin-Bar" TEA Laser]]>

If there is a difference of electric potential between two points in space, since electric potential is electric potential energy per charge, there is a difference in the electric...

What about the electric field in a circuit with resistors?]]>

The work the gravitational force does on the object will be: 9.81N*100m = 981 joules.

Another object with same...

Side kick on a falling object, mechanical energy and work]]>

How can one calculate the duration of fall of an astronaut "lost" to 20 m of his shuttle? We can assume that they are stopped at the beginning of the fall.

I do not see how.

Dylan]]>

I need some basic understanding between theory and practical with respect to blowers.

Blowers usually come with blower curves which give a relationship between Static Pressure and Flow. Usually, SP is inversely proportional to Flow, as in SP increases as flow decreases. Example of a...

Blower/Fan Curves]]>

Phase/group refractive index and reflection]]>

If so, is there some name for that which is smaller? Is there some fundamental measuring unit that...

Question About Planck Scale Unit]]>

So what is Rotational velocity? What does it define? How do signs work with rotation? What does its acceleration mean? Angular Velocity is...

What is Rotation]]>

I read in book that in beta + decay proton decays to neutron

But i can't understand how it is possible if proton mass is less than neutron mass.I read on net but it says 'quarks' and 'd u p' things which i dont study about currently.

Also why it only happen inside...

Explaination of beta + decay in layman language]]>

The person has a bow and arrow. He stretches the arrow on the bow, and then shots the arrow out in the space. Since there are no friction and gravitational force in that space, the arrow will have...

Potential and kinetic force of an arrow shot at space.]]>

This is a question related to an everyday activity .

View attachment 215253

My thinking - The base of the inclined plane is along the x axis and it makes an angle θ with positive x axis .We are looking from the +z axis .

There will be three forces acting on the person . Weight ,...

Walking up an inclined plane]]>

- Are there experiments that will demonstrate (a) there is an electric field present? Stark effect? (b) a magnetic field, (c) that they are...

Electromagnetic waves/radiation properties?]]>

In thinking about vision, especially color vision, I understand that color as such is not a real property of the external world. Nor for that matter...

Why "light"?]]>

I'm firing alpha particles at a gold film, given that the plum pudding model is the pinnacle of human understanding of the atom, meaning I believe matter is made of...

Gold Foil Experiment]]>

Escape velocity and kinetic energy of the Earth]]>

Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N.

Here's the confusion:

By using the non-conservative force work energy...

Non-conservative work energy theorem and potential energy]]>

Time can be divided into smaller amounts of time.

So, 1 second can be divided into 1/2, 1/4, 1/6 etc seconds

SO, 1 second can be divided into 1 / infinite amount seconds

So, it follows that this will yield an infinitely small amount of time.

So, given that there is an...

How does time go forward?]]>

I have equation: View attachment 214965 and I need to find the value of parameter A at which the homoclinic bifurcation occurs.

I know, that in this case A=-0.34, but I solution, how to find it.

Can you help me, what numerical method I should use to find A?...

Critical value of homoclinic bifurcation]]>

In an even very simple geometry we see a constriction or rather offset of the Proton flux at surfaces (surface 1118,...

MCNPX Mesh Tally Problem: Offset of proton flux at surfaces]]>

Question about speed and vehicles]]>

https://www.wired.com/story/how-to-hoist-yourself-out-of-a-hole-with-physics/

Remember folks: Don’t try this at home as you may be late for dinner.]]>

Coalesced drops form a bigger drop and there is extra energy spare.Now this energy is said to give kinetic energy to bigger drop.Which factor decides the velocity of coalesced drop?

Is it just any accidental push after coalescence?

I think also that the process is just feasible...

Coalescence of drops]]>

Magnetic Energy = 1/2LI^2?]]>

This YouTube video shows various shapes of pyrolytic graphite suspended on an alternating polarity matrix of square neodymium magnets.

View attachment 215195

As I understand the principle of diamagnetic anisotropy, the stronger the external...

Diamagnetism & levitation of pyrolytic graphite explanation]]>

I have a problem here. I dont get why the stagnation pressure equal the height of the water in the pitot tube.

The liquid manometer is easy. We analyse the forces on the horizontal contact surface of the tube and the liquid manometer so P1 = Density * g * h...

Pitot tube]]>

Please tell me if I should provide more information, i'm pretty new to this.]]>

How does vibration affect the Higgs field interaction?]]>

This may be an incredibly simple question, but I am looking for some help to clarify things for me.

I am a researcher interested in animal locomotion. Currently, I am working on a project collecting single limb force data (vertical, horizontal, and mediolateral substrate reaction force...

Predicting the vertical/horizontal/mediolateral force of a lungfish limb]]>

As a crude analogy, when wind blows in the face of a windmill, we can intuitively see why it rotates clockwise or counterclockwise. It is because of the...

Why do electrons obey Fleming's left hand rule?]]>

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

Physics Learning Resources]]>

How can X-ray energy transitions be identified?]]>

Having Trouble Finding G-Force of an Impact -- Details in post]]>

Output of a half wave rectifier]]>

Self-Induced Emf and Angular Frequency]]>

Please, I learned that a wave is something the photons "surf" on, like, in one electromagnetic wave, can have many photons.

So, is this true? Like, I though that one gamma ray and an infrared photon would ride different waves...

More: the light from the...

The relation between photons and waves]]>

Now I was wondering how this formula could be applied to continuous matter. Let us imagine a very simple case where we...

Gravitational potential energy and continuous matter]]>

Why do neutron stars have such powerful magnetic fields?]]>

Quantifying Static Electricity Hazard with High Explosives]]>

I'm trying to get a conceptual understanding of why switching gears makes pedaling easier or harder. I think I understand what's happening with the

Let's suppose our...

Bicycle gears, force, torque]]>

Sorry for my English...

I have made some calculations. By Iterative calculation. With Excel.

The time that need two objects to fall from 10 meters to 2 meters.

The mass of the objects i choose are:

1 and 10 kilos.

2 and 10 kilos

5 and 10 kilos.

And.

1 and 9 kilos

3 and 7 kilos.

5 and 5...

Duration of a fall]]>

Dimension of human perception]]>

Please critique the following logic...

When a runner hikes/runs to the top of a mountain, the chemical potential energy inside the muscles transferred into the potential energy of the runner's body mass at the higher elevation (Pe = mass*gravity*height = mgh). Energy is...

Energy transfer during uphill vs downhill running]]>

My job is to perform a stress analysis to determine the regions of maximum...

How can I draw a free body diagram of a rotating wheel?]]>

Real objective time clock/s?]]>

I want to get quantitive value about that problem.

What would be the kind of wave or EM field that could heat human tissu of 1°C in (say a body part like the thigh), say in one hour, at a distance of 2m ?

We could...

Energy of beamed EM field that can heat human tissue]]>

To illustrate the...

How do I name a generalisation of the wave equation?]]>

Can there be a subquantum level?]]>

Basic question on atomic forces]]>

what will be the time period of oscillations??]]>

In 1815, Fresnel made, with Arago, the experience of Poisson spot. (or

Light experience.]]>