# All Questions

18k views

### What does the magnitude of the acceleration mean?

I am a little confused as to what the magnitude of acceleration is and what it means.
21 views

### Recommend books on mechanics, motion and it's laws [duplicate]

I want a book that discuss all these things practically. I don't require it for any exam. Just for applying it confidently anywhere (want to Analyse fluids,thermo etc.) Want a book that explain how to ...
150 views

### Without apparatus can we say that the system is measured(decohered) by the environment?

"Einselection" and "tridecompositional uniqueness theorem" seem to resolve the preferred basis problem. But the premise is that there are three parts in discussion.(system, apparatus, environment) ...
28 views

### Separating the potential energy of a system of particles.

Assuming all forces derive form a conservative source and that all forces observe the strong form of the third law, how do we arrive at the following equation? V=\sum _i V_i+\frac ...
9 views

### Is there a difference between spring fatigue and plastic deformation in springs?

Is there a difference between spring fatigue and plastic deformation in springs? Plastic deformation means permanent deformation in springs caused due to stretching in springs.
16 views

### Finding voltage between two points in space

If electric field vector is defines as : $\vec{E} = \frac{V_0x^2}{a^3} \vec{i_x} + \frac{V_0y}{a^2} \vec{i_y}$ where $V_0$ and $a$ are known constants, $\vec{i_x}$ and $\vec{i_y}$ unit vectors of ...
310 views

### Underdetermined forces in a statics problem

I was trying to cook up a good exam problem on Newtonian mechanics, and I came up with one that I didn't fully understand myself. Always fun when you can outsmart yourself. In the figure a cylinder ...
33 views

### When referring to weights and mass of weights in a physics laboratory, do we use the term mass or weights?

What terminology is used to refer to weights/ mass/ weight of mass/ mass of weights when referring to the mass of weights in a physics report? My question is more of the weights that we use in the ...
170 views

### Topology of phase space

Context: From Liouville's integrability theorem we know that: If a system with $n$ degrees of freedom exhibits at least $n$ globally defined integrals of motion (i.e. first integrals), where all ...
52 views

### What is discrete phase space?

I've been reading a little about the usual, continuous Wigner functions and phase space quasi-distributions in general, and I believe I understand the idea behind them. The Wigner function arises when ...
513 views

### Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
769 views

### How does Hendo hoverboards achieve the self-propelling motion? What is the MFA?

From what I understand of the idea behind Hendo hoverboards, they use four disc shaped hover-engines to generate a self-propelling motion. I also understand that it uses Lenz's law and eddy currents. ...
151 views

### Can capillary forces be used to make hydro electricity?

Could a device with very thin columns of glass or something that attracts water more be used to pull water up and then release it to drive generator and perhaps add vacuum. I have been wondering ...
45 views

### What is the simplest way to perform a Cavendish experiment?

The Cavendish experiment is cool, but seems complicated to experimentally perform. What is a simple way to recreate the experiment?
48 views

2k views

### Why are objects at rest in motion through spacetime at the speed of light?

I read that an object at rest has such a stupendous amount of energy, $E=mc^2$ because it's effectively in motion through space-time at the speed of light and it's traveling through the time dimension ...
1k views

### What problems with Electromagnetism led Einstein to the Special Theory of Relativity?

I have often heard it said that several problems in the theory of electromagnetism as described by Maxwell's equations led Einstein to his theory of Special Relativity. What exactly were these ...
49 views

### What is the longitudinal difference between the sub­solar point and the magnetic poles at time $t$ (hours)?

I'm trying to convert geomagnetic coordinate to geographic, but there are some steps in the paper which I'm reading, that I don't understand. I have the geomagnetic latitude centered around the ...
42 views

### Space elevator: a Earth rotation brake model

I read this article regarding the space elevator. A very long carbon nanotubes string, running from the Earth surface into the vacuum of the space. Tension and friction, an enormous quantity of ...
52 views

### Is the decay $B\rightarrow K^* \gamma$ decay allowed in the Standard Model?

This is my idea of the Feynman diagram of the $B^0$ to a $K^0$ decay: The photon is radiated off by one of the particles, and by $up$ quarks I just mean ($u$,$c$ and $t$) and their antiquarks. how ...
95 views

### Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?

From the Gross-Pitaevskii equation $$i\hbar\frac{\partial\psi}{\partial t}=\left(-\frac{\hbar^2}{2m}\nabla^2+V+g|\psi|^2\right)\psi$$ using the variational relation ...
23 views

### Extract particular ions from an ionized gas

Is it possible to extract any particular ion ( either positive or negative ) from ionized gas ( or plasma ) without spending any ...
99 views

### What is the relationship between force and momentum in collisions?

I know that $\Sigma F = \Delta mv/\Delta t$. But if we had a marble that moves in a straight line at a constant velocity and colloids with another marble. Because of the law of conservation of ...
129 views

I took an empty clear sphere with radius r, put some weight inside this sphere, and put in into the water. I calculate the buoyancy force as: Volume of the sphere = Volume of the water displaced ...
426 views

### What's wrong with this application of Thomas Precession to circular motion velocity measurements?

If you happen to have the Third Edition of Classical Electrodynamics by John David Jackson, turn to section 11.8, as that's where I'm getting all this from. If not, you should still be able to follow ...
34 views

### Flea jumping question [on hold]

During takeoff, a flea develops an acceleration of $3m/s^2$. It reaches a max height of 36mm. How long does this acceleration last? Finding the initial velocity was fairly easy, but finding the time ...
292 views
+50

### Why does a conservative force return the work done against it by a body to that body?

Newton's 3rd law of motion: Newton's third law of motion or the law of action and reaction implies that there is no isolated force in nature. Whenever there is any force at all , there must be ...
12 views

### How to drive quadrotor moments of inertia

I would like to know how moments of inertia (i.e. around x,y and z axes) of a quadrotor is driven given the total mass and the distance from the origin of the quadrotor to the center of a $i$th ...
25 views

### Speed with wind resistance

This is probably a basic question, but it has been a while since I did anything like this. If a boat is sailing forward at speed $x$ and the direction of the wind, with magnitude $y$, is either equal, ...
3k views

### Homemade salad dressing separates into layers after it sits for a while. Why doesn't this violate the 2nd law of thermodynamics?

The oil, vinegar and other liquids in homemade salad dressing separate into layers after sitting for a while, making the mixture become more organized as time evolves. Why doesn't this violate the ...
16 views

### A box up an inclined ramp with a coefficient of friction [on hold]

A 6.25 horsepower motor to pull the boxes a distance of 8.35 meters up a ramp inclined at an angle of 36.2º with respect to horizontal. The boxes have a coefficient of kinetic friction of 0.381 as ...

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