0
votes
3answers
248 views

The metric expansion of space and Hawking

In a Wikipedia article I read that the "Metric Expansion of Space" exceeds the speed of light. If this is true then we must be being disconnected from very remote parts of the universe since gravity ...
0
votes
1answer
206 views

Spectroscopic notation $s$, $p$, $d$, $f$, $\ldots$

$s$ is sharp, $p$ for principal, $d$ for diffuse, $f$ for fundamental. Where do all those term come from? I do not see any link with the corresponding shapes.
0
votes
1answer
113 views

Is it safe for astronaut to do this “dangerous” movement?

So, if the astronaut is working outside the space station in thew space, could he not tie himself onto the space station and if he is going further away of the space station, i think he could just ...
0
votes
1answer
152 views

How was Dorsey able to measure speed of light with 3 significant digits?

How was Dorsey able to measure speed of light with 3 significant digits in the year of 1907?
0
votes
2answers
590 views

Kinematics - concept question

A child tosses a ball directly upward. Its total time in the air is T. Its maximum height is H. What is its height after it has been in the air a time T/4? Neglect air resistance. Ok so I know that ...
0
votes
1answer
48 views

observation and implied time since creation

I read on a post Big Bang and Cosmic microwave background radiation? We detect light from another 13 billion years ago does this mean that one billion years ago we could only detect light from about ...
0
votes
1answer
74 views

Would we feel the rotation of a rotating habitat?

Assume that a space habitat is shaped like a can with the "top" open. lets say we attach the can's top to a string with an astronaut standing on the base. We then rotate the can in deep space using ...
0
votes
2answers
4k views

Why does a parachute decrease terminal velocity?

Terminal Velocity depends on two things- surface area and speed. These are inversely proportionate. If both these variables affect terminal velocity, why do parachutes slow you down? Initially you ...
0
votes
3answers
329 views

Can I get anions by touching the negative electrode of a battery? [closed]

It is said that anions are good for health. Instead of using an anion generator, can I get anions by touching the negative electrode of a battery?
0
votes
2answers
101 views

Dilation invariant lattice

In one dimension, we can define the lattice $ f(x+a)=f(x) $ so the lattice is translation invariant. But, can we give a lattice so $ f(p^{k}x)=f(x) $ for ALL the primes $ P= 2,3,5,7,11,....$ and ...
0
votes
1answer
150 views

“Conceptualizing” neutrinos

Layman here. EE and BS physics. I am "content" in viewing photons/electromagnetic radiation as an "emergent" property of spacetime? due to the electrons ("particles..?") and all their activity jumping ...
0
votes
2answers
6k views

How do I calculate output voltage from a given supply voltage and resistance?

I have searched everywhere but I can't seem to find out how I can calculate the output voltage (or voltage over a component) from the resistance of a resistor (or other component) and the supply ...
0
votes
2answers
392 views

How to find that a molecule has zero spin?

I read that Ne has $S=0$. How can this be found, knowing the electron configuration? Electrons, protons and neutrons all have 1/2 spin. The Pauli exclusion principle implies that the even number of ...
0
votes
2answers
266 views

What is the interaction with Higgs field(s) that give the quarks so much different masses?

The masses of quarks are: mu 2∼3 MeV md 4∼6 MeV mc 1.3 GeV ms 80∼130 MeV mt 173 GeV mb 4∼5 GeV
0
votes
2answers
2k views

Jumping in an elevator?

I've always been under the impression that jumping in an elevator wouldn't help at all, especially after reading a snippet of physics where Einstein said that free fall was identical to zero gravity. ...
0
votes
2answers
191 views

Identifying hue, brightness and chroma of color and reaction time

If someone knows how identify hue, brightness, and chroma of color, please let me know. I am a PhD student at Educational Linguistics UNM.
0
votes
2answers
383 views

Statistical interpretation of Entropy

I'm preparing my statistical physics course, and while writing the lecture notes it says that a system with non distinguishable particles has much less microstates asociated with a particular ...
0
votes
3answers
252 views

Learning physics conceptually for a layman [closed]

Can anyone suggest a video or book that will allow the layman to grasp physics concepts in a conceptual manner?
0
votes
1answer
169 views

I think I disprove this with kinematics, but energy says it is right

! Here is my kinematics argument. For now I am only going to look at ball 2 and ball 3. Make note of the following data. $|v_0| = 10m/s$, $y_0 = 10m$, $\theta_2^0 = 30^0$, $\theta_3^0 = -45^0, g = ...
0
votes
3answers
840 views

Who is right? Force exerted on a body. Me or my friend?

Three masses $m_1 = 3\text{ kg}$, $m_2 = 9\text{ kg}$ and $m_3 = 6\text{ kg}$ hang from three identical springs in a motionless elevator. The elevator is moving downward with a velocity of $v = ...
0
votes
2answers
777 views

Electric field problem

First of all I hope I'm doing the right thing by posting this message on the stack exchange site. I know you aren't my personal problem solvers, but I just can't solve it. And maybe this problem is ...
0
votes
2answers
427 views

How to calculate total distance and time a puck will move?

To simulate a puck's movement, I use the following model (please restrain from discussing the model, it makes the simulation look the way I want it to) and would like to know how to calculate the ...
0
votes
2answers
283 views

Combined Translation and Rotation of a disk possible? material and references?

I am considering building a robot that can rotate and move at the same time. Since it's just a theoretical idea at the time and I need read up material, I thought I would ask here. I am thinking of a ...
0
votes
2answers
154 views

Synthesizing elements (Nuclear Physics/Alchemy?)

Based on my limited knowledge of nuclear physics, it seems that one day it may/will be possible to synthesize whatever elements we may need, given enough energy. Is this accurate? Is there a table ...
0
votes
2answers
132 views

Epistemologically, can we ever deduce the 'true' theory of everything? [closed]

Operationally, we can only know about the results of experiments and observations. From them, we can conclude our world is one which is complex enough to allow for computers. After all, we're using ...
0
votes
2answers
900 views

Understanding Black hole information paradox?

I am not a physicist, I am a enthusiast trying to understand thinking behind "Holographic Principle" by Leonard Susskind. Recently I saw program on DS Through the wormhole - The riddle of the black ...
0
votes
1answer
2k views

What color a transparent object reflect?

We say an object's color is blue if the object is opaque, reflects blue color and absorbs waves of other color. What color a transparent object actually reflects?
0
votes
1answer
149 views

About the energy with the repulsive potential

Consider the reduced radial Schrodinger equation: $$-\frac{1}{2}\frac{\text{d}^2}{\text{d}r^2}\phi(r)+V(r)\phi(r)=E\phi(r).$$ We try to find a bound state (i.e. $\phi(0)=\phi(+\infty)=0$). Here ...
0
votes
2answers
1k views

Negative g-force: difference between gravity and centrifugal force?

I was having a discussion with a friend about human tolerances of g-force. He believed that the maximum human tolerance of negative g-force is low, in the order of .5 g. I countered, saying that ...
0
votes
3answers
193 views

What is the volume of a parcel of air of a giving weight at average sea level pressure

I know this is probably some basic math once you have the figures, but my Google-fu is failing me. Say I have 5 pounds of air. Air meaning, the typical composition of the atmosphere of Earth. And by ...
0
votes
2answers
738 views

What happen when a gas is being heated far beyond its boiling point?

let's say we pour some water to the Sun. Or boil water on 2000 degrees Celsius on Earth.
0
votes
1answer
192 views

My computer turns on when it “sees” me [closed]

Before asking, I swear that, for how it may seem strange, this is all true. Very briefly, when my pc is off and I am near it, it turns on. I do not touch anything. Nobody else have the same effect. I ...
0
votes
2answers
614 views

Why is travelling around the speed of light a problem?

I don't fully understand what would happen if we could travel at the speed of light. But I saw somewhere here that it would mean events happen out of order. But why is this a problem. It is said that ...
0
votes
2answers
3k views

Does an Increase of Force affect the Speed of an object if the acceleration stays constant?

If I had a mass of $100\:\rm{kg}$ accelerating due to gravity, using $F=ma$: $F = 100\:\rm{kg} \times 9.8\:\rm{m/s^2}$ $F = 980 \:\rm N$... If I increased the mass to 200kg, the force would be 1960 ...
0
votes
2answers
330 views

Do and can phone signals come inside AC car which is glass-packed

Can phone signals penetrate glass, so can I expect phone signals to come if I am sitting inside a closed AC car. Thanks,
0
votes
2answers
434 views

Casimir effect plate experiment

i was a little confused about the casimir effect. my understanding is with the 2 plate experiment there was a force pushing the plates together because there were less virtual particles in between the ...
0
votes
1answer
173 views

Quick question on the ionization energy and the selection rule

So I am looking through my book and it says ".... the order of the excited states is exactly the same order (3p-4s-3d-4p)". But now I am looking at a question in the book and it says "Is 3d to 4s ...
0
votes
2answers
2k views

Forces in a Pendulum

Help me visualise the forces found in a pendulum. I know weight can be decomposed into $F_x$ and $F_y$. Centripetal force, acceleration and velocity are three words that I'm confused. Centripetal ...
0
votes
1answer
640 views

Proving Operator identities (Quantum Physics)

How would I go about showing: $$\hat{A}^{\dagger} + \hat{B}^{\dagger} = \left( \hat{A} + \hat{B} \right) ^{\dagger}$$
0
votes
3answers
1k views

Direction of Magnetic force from a current running through a coil of wire

What is the direction is the magnetic force vectors pointing from a coil of wire that has current running through it? ...
0
votes
5answers
1k views

What is the most energy efficient way to boil an egg?

Starting with a pot of cold tap water, I want to cook a hard-boiled egg using the minimum amount of energy. Is it more energy efficient to bring a pot to boil first and then put the egg in it, or to ...
0
votes
1answer
642 views

What is the influence of the nuclear leakage in Japan

The recent news says that Japanese authorities confirmed Saturday that radiation had leaked from a quake-hit nuclear plant after an explosion destroyed a building at the site. What will be the ...
0
votes
2answers
302 views

vector cross products

Lets say you have a free particle in a rotating frame of reference with constant angular velocity $\mathbf{\omega}$. By free, I mean there are no real forces on it. Lets call the moving system ...
0
votes
1answer
179 views

Standing Wave: How to show that $\frac{\mathrm df}{f}=0.5\frac{\mathrm dF}{F}$ where $f$ is frequency and $F$ is tension of the string?

How to do this? Show that if the tension $F$ in a string is changed by a small amount $\mathrm dF$, the fractional change in frequency of a standing wave, $\frac{\mathrm df}{f}$ is given by: ...
0
votes
4answers
217 views

Calculating electric field

This problem is giving me a lot of problems. So $E=k*q/d^2$. We'd want to find the distance from q1 to P, which is .1 meters (not cm) using pythagorean thereom. So we know k, which is just $9x10^9$ ...
0
votes
2answers
707 views

How is electrical energy transmitted?

My original question was in an effort to understand the electrical analogy to Markov chains, which is explained in Snell's article. There are some neat parallels that involve taking a Markov chain ...
0
votes
1answer
1k views

Explanation of the experiment with Mach–Zehnder interferometer (self-interference of a single photon)

Here is the description of experiment which uses Mach–Zehnder interferometer http://en.wikipedia.org/wiki/Mach-Zehnder or http://departments.colgate.edu/physics/research/Photon/root/ajpbs02.pdf ...
0
votes
5answers
929 views

Is gravity a vector or tensor function and does gravity have velocity or is it instantaneous?

If gravity exists quantumly it must take up space, have frequency, velocity, etc. Perhaps gravity is too fine a frquency for detection.
0
votes
1answer
16 views

Why the crest of water absorb more light than the trough of water?

I have done my experiment using water ripple to study the behavior of waves. I know that the crest will absorb more light than the trough so that the image created on the white paper sheet appeared to ...
0
votes
3answers
55 views

Why don't the kinematic equations agree with calculating velocity one second at a time?

A car is moving at a velocity of $10 \, \text{m}/\text{s}$. After point $A$ no acceleration is provided. By simple measurement, the acceleration is found to be $-1 \, \text{m}/\text{s}^2$. Using ...

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