# All Questions

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### Acceleration of a unit vector in the Feynman Lectures

In the Feynman Lectures on Physics chapter 28, Feynman explains the radiation equation $$\vec{E}=\frac{-q}{4\pi\epsilon_0 c^2}\, \frac{d^2\hat{e}_{r'}}{dt^2}$$ The unit vector $\hat{e}_{r'}$ is ...
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### Why did we see intereference from a single point source?

In class we were doing an experiment where an agitator was used to create spherical waves on a ripple tank. I noticed that when using only a single paddle (so a single point source) that you could see ...
1answer
57 views

### Is it possible that matter/antimatter collisions emit resonance frequencies of H/He?

Is it possible that matter/antimatter collisions emit resonance frequencies of H/He? I am researching a high energy phenomenon that occurs between the frequencies of 1200-1580 MHz. This come from a ...
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### Distance between Newton's Rings fringes is does not seem linear

On the outer edges of Newton Ring patterns, the fringes are really close together, and much more uneven. Also, the spacing does not seem to decrease linearly at all as you move from the center. Why is ...
0answers
81 views

### A force applied to an inclined plane

Below are two drawn diagrams of the problem with some explanation. Note: I think my notation for the force that the block exerts on the plane in the horizontal direction is not the standard ...
2answers
381 views

### Relations between pressure and temperature

I have several questions concerning thermodynamics and I order them in 4 points that may be related: What's the difference between heat and work at the atomic level? Isn't heat simply work between ...
0answers
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### Electrodynamics using exterior calculus

Can anyone suggest resource for full course of electrodynamics using exterior calculus?
2answers
107 views

### What materials are used in non thermal plasma?

While reading about non-thermal plasmas, I came across their ionization potentials(~1%), and other capabilities, such as their non Maxwellian energy distributions. At what temperatures, and pressures ...
1answer
677 views

### A two-dimensional event horizon?

Today, I came across an article which says that the Universe began with the collapse of a 4-dimensional [spatial] Universe. Well, I don't know if there's any way to confirm these like it is with all ...
1answer
82 views

### Understanding EM Fields

I am an electronics engineering major and some questions arise when studying communications technology that utilizes wireless technology. In particular, I am more of a complete picture kind of person, ...
2answers
163 views

### Looking for lists of student difficulties with electromagnetism, circuits (DC and AC)

I'm trying to help with an Instructor's Guide for an introductory calc-based physics text, and it would really help if I could locate some lists of typical student difficulties with topics like ... ...
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### The inverse square law of sound through solids?

We all know about the inverse square law of sound. In short the power of the wave will get evenly spread on an ever increasing spherical expansion and this will dissipate the power of the wave at a ...
3answers
3k views

### Potential difference (PD) and electromotive force (EMF) in terms of electrons?

I am trying to understand potential difference and electromotive force in terms of electrons. In the above 3 circuit diagrams the red shows (what I think to be) the distribution of electrons ...
1answer
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### Force and torque on rigid body in space

Assume that we have two disks in space. If we act same force F on each disk like above figure, how they react? I first thought that since $F_{ext}=\frac{dP_{cm}}{dt}$, the CM(center of mass) ...
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A uniform rod of mass 1.2 kg and length 1.8 m is pivoted in the horizontal position as shown (black point). The rod is at rest and then released. The acceleration due to gravity is $g = 9.8 ... 3answers 230 views ### How could we define speed without time? This is a bit of a brain twister but it's a very serious question. Please be precise in your answer. I do not believe time exists. I believe it is simply an illusion of our perception, the ... 4answers 162 views ### What experiment would disprove Friedmann model of cosmology? What experiment would disprove Friedmann model of cosmology? As a layman, I have read a lot of articles and threads in specialized forums. I am probably wrong, but I developed an impression that that ... 0answers 45 views ### How the Bloch sphere of a Hahn echo in NMR looks like? 90-t-90-t-echo I have tried to find in the literature a proper nice and beautiful Bloch sphere to describe the trajectory of a nuclear spin, starting in z-axis, using a pulse sequence of an initial 90º pulse with ... 2answers 2k views ### Unit of gradient/slope? So I have a graph: The value of the gradient/slope is$1.6±0.4$and the value of the intercept is$0.9±0.4$. But what are the units of the graph? Is the unit of the gradient$v^2M^{-1}$? What about ... 2answers 233 views ### How much work will a human do to lift a weight? I saw a pretty simple homework question here that asked how much work it takes to lift a 200 kg weight, and while the math for a basic answer is simple the weightlifter in me instead wanted to ... 1answer 106 views ### My orbiting body is orbiting about the wrong focus of it's elliptical orbit… why? I am coding in c++ and am computing the position of an orbiting body as a function of time. Everything is almost working. I have a nice elliptical orbit. Except, my orbiting body speeds up as it ... 2answers 119 views ### Is the mechanics of the wave function in the quantum mechanics deterministic? Is possible a non-deterministic propagation of the wave function in the QM? 1answer 38 views ### How can I ensure my scale is not affected my surface beneath it I have person weighing spring scale. I live in Japan where the house has wood floors which deflect significantly under weight. I weighed my self in the bathroom and in the tiled bath area. The ... 2answers 344 views ### Energy stored in a capacitor in an RC circuit Suppose we have a capacitor of capacitance$C$and a cell of emf$E$, why is the maximum energy stored in a capacitor equal to$\tfrac{1}{2}CE^2\$? I feel confused because, the potential difference ...

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