# All Questions

20 views

### What forces are involved to enable a rock to skip in water?

Does the surface tension matter or is it something else that is providing the upward force? Can someone explain the phenomenon to me physically?
43 views

### Why is steel-reinforced concrete stronger than ordinary concrete?

Is it only because steel has higher elasticity? What other factors are involved?
64 views

### Vertical Travelling - Taking Advantage of Earth's Rotation [duplicate]

As per our current scientific knowledge the earth rotates on its axis and it rotates at a speed of 1670 kilometers/hour. This decreases by the cosine of your latitude so that at a latitude of 45 ...
28 views

### Why is it that in a warm shower water feels hotter near the head?

When the water first hits your body, it feels warmer than when it streams down towards your feet. I realize that part of this is due to the water cooling down by dissipation to the surrounding as it ...
33 views

### Solving equation of motion with exponential friction term

My friend's kid asked me this question. I have no idea how to solve it since I have stopped calculating mechanics for about 15 years since I graduated from high school. The question is: A boat that ...
27 views

### Why do some ionic compounds form in the NaCl structure vs the CsCl structure?

Everything else the same, I'd expect two monoatomic ions to form an ionic structure in the CsCl structure because with more atoms bonded to each atom, it would seem to be more stable. And yet I ...
27 views

### Can you get a static shock in a vacuum if you are not touch the object?

For example when you hop on a trampoline sometimes you will be shocked before you even touch the tramp. Does the shock have to pass through the air to get to you or can it work in a vacuum?
9 views

### What are the limiting conditions for one side of a charged parallel plate capacitor to discharge to ground [duplicate]

@annav Earlier I asked a similar question with full description but the stackexchange system put it on hold. It is entitled "to annamitra palit re capacitor discharge" . I am stumped by the fact ...
26 views

### Rabi oscillations with quantized light: which is the “quantum” effect, collapse, revival or both?

In wikipedia http://en.wikipedia.org/wiki/Jaynes%E2%80%93Cummings_model#History it is stated that It was later discovered that the revival of the atomic population inversion after its collapse is ...
523 views

### Why can I see my breath after I pop my ears?

I have this weird but reproducible thing that I can see my breath for less than a second even in hot/humid weather. The key to do that is to pop my ears - I have to do that often, it's like I'm on a ...
212 views

### Advanced kinematics problem regarding $F = ma$ [on hold]

I really need help with this problem. Thank you for your time. Question: Look at the figure below. Derive the formula for the magnitude of the force F⃗ exerted on the large block (mC) in the ...
30 views

### A ball is dropped from the roof of a building. How fast is it moving after 4.9 seconds? (Absolute value) [on hold]

i really need help. A ball is dropped from the roof of a building. How fast is it moving after 4.9 seconds? (Absolute value) in m/s A water balloon is thrown downward from a tall building with an ...
23 views

### Calculate surface pressure due to forced vibrating plate using wavenumber space [on hold]

My problem lies in the field of acoustics. I have a given complex velocity distribution. The velocity is the velocity in the normal direction to a rectengular simply supported vibrating plate. I now ...
75 views

### How fast until you feel wind in space? [duplicate]

I couldn't find this question asked anywhere else, so I thought I would ask it here: does anyone know how fast you would have to be traveling in space to feel 'wind' from the particles in front of ...
17 views

### Computer coding of Perdew Burke and Ernzerho (PBE) method

I have been assigned the task to write a computer code to implement the Perdew Burke and Ernzerhof (PBE) method. Does anyone know a good reference which can make the coding of this method easier?
66 views

### Chiral anomalies

Recently I have read that there is contraction of chiral anomalies in SM. But people are working on chiral anomalies theory. So I have the question: what is the importance of development of the theory ...
51 views

### A universe from nothing [duplicate]

The more time you spending in measuring your experiment (thus standard deviation will become smaller) the more precisely you will measure energy of this system.... energy time uncertainly principle ...
23 views

### Is there any simulation program for electrostatic and magnetostatic fields? [duplicate]

please can any one suggest me a good program for simulating electrostatic and magnetostatic fields (forces,flux density, energy and potential) ?
28 views

### Can human body survive a negative acceleration of $250m/s^2$ [on hold]

Can the human body can survive a negative acceleration trauma accident because of a sudden stop if the magnitude of the acceleration is less than $250m/s^2$. If you are involved in an automobile ...
26 views

### What is the Fourier Transform of f'(x)/x [migrated]

Is it even possible to find. It's deceptively simple looking. What about f(x)/x?
44 views

### What made Einstein to figure out speed of light is constant? [duplicate]

I have gone through the answers to the questions on the similar lines, but I am not fully satisfied with them, I want to dig deep into this assumption because it is a very strong assumption. If ...
12 views

### Thermal healing of defects in crystals

Thermal treatment can heal point defects due to the diffusion of atoms towards empty points. In a solid crystal structure, atoms do not diffuse at room temperature (correct?) Energy of thermal ...
28 views

### Confusion about Gauss's law for Electrostatics

I just learning about Gauss's law in integral and differential form. There's something I'm a bit confused about: Let $\vec{r}$ be the location of your test charge with respect to the origin, and ...
24 views

### Why does an increase in pressure raise melting point?

I've heard that if you increase pressure in a system that has ice in it, then its melting point will increase. However, I would've thought that it would decrease the melting point as the ice would ...
14 views

### Flux through planes of a wind turbine [on hold]

The question asks how much wind will flow through each plane of a cube surrounding the turbine. the velocity of the wind is given by a function that depends on position according to v=(az,bz^2,c). The ...
94 views

### Unitarity and renormalizability

What is the difference between the unitarity of the theory and its renormalizability? Can we say that renormalizable theory is unitary after renormalization? The questions have arisen after I have ...
36 views

### What is the difference between a circuit with a resistor and one without it in energy terms?

In Fundamentals of Physics (HRW), an equation is derived for the current in a circuit in terms of its emf and resistance by the 'Energy method'; that is, deriving emf=i.r and saying that the work done ...
314 views

### Is a causal relationship implied by Newton's 2nd Law? [on hold]

Throughout my time learning physics I have been imbued with the notion that forces cause accelerations, period. Accelerations don't cause forces, and they aren't merely correlated phenomena. By ...
33 views

### How much fuel is needed for a constant-acceleration rocket?

My son and I have been discussing the concept of a constant-acceleration rocket, as described here and here. We're willing to assume advanced technology such as a fusion rocket, which, according to ...
13 views

### Help with Kinematics and trajectory [duplicate]

I am asking this again because it was closed and I didn't receive a response. So a baseball is hit with a velocity of 30 m/s at 42.6 degrees to the ground. A fielder who is supposed to catch the ...
9 views

### Projectile motion help needed [duplicate]

I have a question. So a baseball is hit with a velocity of 30 m/s at 42.6 degrees to the ground. A fielder who is supposed to catch the ball is smart and knows that he is exactly 8 meters from where ...
22 views

### neutrons fission reaction [on hold]

If neutrons are uncharged particles then how they can be bombarded together and continue breaking into smaller and smaller neutrons? If they carry no charge then how it is possible that they can break ...
9 views

### Convex and Concave Bridges forces [on hold]

What are the forces acting on a car when travelling in a concave and convex bridge?
27 views

### Potential Differences (Voltage) from Point Charges [on hold]

Identical +1.8 micro Colomb charges are fixed to adjacent corners of a square. What charge (magnitude and algebraic sign) should be fixed to one of the empty corners, so that the total electric ...
40 views

### To Annamitra Palit re capacitor discharge [on hold]

@Anamitra Palit , I have read the discussion of 2012 re discharge of a parallel plates cap to ground from one pole, and was quite confused. So I made a series of experiments charging a 1 microFar cap ...
48 views

### Timelike curves in Special Relativity

I have a question that probably might sound silly to most of you. We know that a natural Lorentz-invariant parametrization of a timelike curve is provided by: $$\tau$$ the Lorentz-invariant proper ...
169 views

### On deriving Schrodinger Equation

I do know that one can't actually derive any axiom, but here is my serious attempt to explain Time Independent Schrodinger Equation with minimum preliminary knowledge. In the following $f$ is ...
15 views

### What is the best angle to see water

Sometimes when I clean my house, I miss some of the water since it seems invisible, but when I stand in different angle from the water I can see it clearly, whereas some angles offer partial ...
21 views

### Problem in ray diagrams in convex mirrors

I just found out about the Desmos online graphing calculator, and it is really a very nice tool. Just while playing with it, I had the idea of creating simulations. I decided to make a simulation of ...
22 views

### Why eigenvector points to principal stress plane?

I can represent a tensor by a matrix. Suppose we are talking about a 2nd order tensor, and the matrix is therefore 3x3. If I find one eigenvector of that matrix; that vector represents normal vector ...
18 views

### pressure drop in venturi [on hold]

Recently was taught Bernoulli's principle and am confused about visualizing how pressure drops in the venturi. It seems a reduction in the diameter of the pipe causes static pressure to increase ...
29 views

### What is physical significance of product of Inertia? [duplicate]

I have read in available sources that product of inertia is just a term that is defined because it is useful in calculating the minimum and maximum moments of inertia of a body and also in finding the ...
60 views

### Has the universe we live in started as a black hole that is imploding?

As discussed in this question, as far back as the 1960s it was suggested that the Schwarzschild metric can be smoothly joined to a de Sitter metric. For example the idea has been used by Lee Smolin in ...
28 views

### Left (right) invariant vector fields on superspace

I read Freed'd book on "Five lectures on supersymmetry". For any vector space $V$ with metric of signature $(1,n-1)$ he constructs super Lie algebra $$L=V \oplus S^*,$$ where $S$ is space of ...
29 views

### Difference between high-level and low-levels of electromagnetic radiation

can someone please explain me what we mean by 'high-level' or 'low-level' in electromagnetic radiation? for example, it is believed that high-level microwave radiation is harmful to human but not the ...
41 views

### DC Generator with magnet as rotor

DC generators convert the AC current in them by split ring commutators right and the graph of the current will be like this but the question is how would be the graph if the magnet is the rotor and ...
118 views

### How should I quote errors when measurements are asymetrically clustered?

Suppose five people measure the length of a stick and report the following values 4.90cm 4.92cm 4.93cm 4.94cm 4.94cm In high school science we are told that in ...
64 views

### Why is graphene the only (stable) 2D sheet structure?

I know that Carbon molecules can form different structures depending on how they bond with each other: graphite, diamond, graphene and fullerene. As far as I understand, graphene is just a "sheet" of ...