# All Questions

88 views

### Physics major in university [on hold]

When I was 10, I started reading college-physics books; I always loved physics. I'm 17 years old and, on my own, learned calculus, real analysis, complex analysis, functional analysis, differential ...
24 views

### Few doubts about saturated vapour pressure and unsaturated vapour pressure

I have some sort of confusions towards saturated vapour pressure and unsaturated vapour pressure.. So let me give you those. What is exactly saturated vapour pressure and unsaturated vapour ...
16 views

### Anomalous diffusion dynamic exponent calculation

I'm trying to calculate this $\alpha$ (dynamic exponent, I think) from an equation from this wikipedia article. The equation (anomalous diffusion power law): $r^2 \propto t^\alpha$ The problem is ...
89 views
+100

### Approximating a target operator

I was wondering if anyone knew how the author got to equation 12 on page four of this paper, I will attempt to explain the situation below. Given $C$, a target operator, we wish to create an ...
9 views

### How do I get 50 Reputation? [migrated]

I was going to comment that the atmosphere takes about 1/3 to 1/2 the mussel velocity based on my 1987 paper on the Flight of Passive Launch Vehicles. I am about to re-do the paper and am working from ...
33 views

### Torque Approximations Neglecting Friction

Disclaimer: I'm not asking for homework help. I don't understand how my calculations work out conceptually. If you can help me understand the connection between the concepts, I'd really appreciate it. ...
52 views

### What would happen if there was no friction on earth? [on hold]

I'm not talking about zero-g or a vacuum. If oxygen, gravity, air pressure, etc still existed but if there was suddenly no friction, anywhere.
10 views

### Particle aggregation: difference between coagulation and coalescence?

I know there are different processes involved in particle aggregation, and that depending on temperature and other factors one of them may be more significant. I know that particles can aggregate, ...
22 views

### How do I incoporate gyro information in my position and velocity calculation? [on hold]

The velocity in 1 direction can be calculated as : $V_t=V_0+at$ And position could be calculated as $P_t=V_0t+1/2at^2$. Besides time, acceleration, I was also given information from 3 axis ...
26 views

### Can I interpret Avogadro's principle of gases from the state equation (ideal gas law)?

Considering the molar form of the ideal gas law I can solve for the ratio of some gas volume, $V$ divided by the number of gas particles, $n$ in mols $$\frac{V}{n}=\frac{RT}{P}$$ And $R$ is the ...
46 views

### Julia in computational physics [on hold]

What are the benefits and drawbacks of using Julia in developing physics models? Traditionally, C/C++ and Fortran (and some Java) have been used in any serious computational physics projects, while ...
15 views

### Are x-rays in fusion plasmas mostly from collisions with high atomic number ions?

Say you have a hot (100eV-1keV) hydrogen plasma with no impurities in it and no collisional interaction with the wall. Would this plasma radiate x-rays? X-rays are from bremsstrahlung, so could ...
18 views

### Which features effect on the Reflection of things?

I'm working on something and I need to find a wire that doesn't reflect well. so, I know one feature is the color of the wire to decrease the reflection. But what other features effect on the ...
56 views

### Why do high voltage transmission line workers need a Faraday cage suit?

In this video the high voltage transmission line workers are wearing a Faraday cage suit. Why is this needed? Without the Faraday cage, the resistance of the human would be very high compared to the ...
46 views

### For an event that can occur in many ways, why is the wavefunction of the event the sum of wavevfunction for each way separately?

The wavefunction of identical particles is given as: $$\psi_{1,2} (x_1,x_2) = \psi_1(x_1)\psi_2(x_2) + \psi_2(x_1)\psi_1(x_2)$$ . Why is it so? Why is it the sum of the two states? What is the ...
75 views

### What does cross product mean in simple words? [migrated]

Two numbers 3 and 4 their multiplication is each one from the first number is repeated a number of times as the second number i.e. 3 times 4 is (1+1+1) times four meaning 1+1+1+1 + 1+1+1+1 + 1+1+1+1 ...
72 views

### Physical meaning of divergence

While reading the section on Hamiltonian mechanics in Taylor's Classical mechanics, I realized that I didn't fully understand what he was saying when he was explaining why ...
28 views

### Simple Beam Worst Case Scenario

Part 1 If I have a simple beam with two supports and a static load, does placing the load in the center push the beam closest to breaking (catastrophic failure)? Will this be more likely to break ...
122 views

### In QFT how do you write down the most general interactions?

This past year I took a QFT class and I now feel comfortable solving scattering problems, but I am still a bit perplexed by how physicists write down a Lagrangian in the first place. In particular, ...
50 views

### Is weather cyclic?

I'm a sports amateur, and enjoy playing in Ultimate Frisbee leagues in my hometown. In the last years, I've observed some "weird" weather behavior, and wondered if it was some sort of coincidence, or ...
25 views

### Calculating center of mass after movement [on hold]

For this problem there is no change in External Forces so change in momentum to the system is 0. We have a massless boat of length $L$ with a person on either end of masses $m_1$ and $m_2$ Person 1 ...
32 views

### Energy of a system if the nuclear repulsion increases

I have calculated the optimised geometry for a molecule. I have noticed that the energy of the nuclear repulsion increases with each iteration of optimisation. What is the logic behind this?
44 views

### Resistance of a metal sphere

How would you go about calculating the electrical resistance of a sphere when you only know it's radius and conductivity? I know with cables you can use $$R = L/(g \cdot S),$$ but I don't know how ...
### How can i prove that $\frac{d\vec{p}}{dt} = \vec{F_{net}}$? [duplicate]
I could prove that $d\vec{p}/dt = m\vec{a}$, but how can I prove that $\vec{F_{net}}=d\vec{p}/dt$? Is force just defined by this expression? What is the rigorous definition of a general force? In my ...