All Questions

125 views

How can I caculate the time to traverse a distance with the Tsiolkovsky equation?

Using the Tsiolkovsky equation I know what the change in velocity is after burning x amount of fuel. $$\Delta V = V_e \dot\ log(\frac{m_1}{m_1-m_2})$$ $m_1$ is my starting mass and $m_2$ is the ...
36 views

In one scene of the movie "Edge of Darkness", the protagonist uses a device to test the radioactivity of milk in a glass container by placing the device near but outside the container. What is this ...
5k views

What enables protons to give new properties to an atom every time one is added?

How does adding one more particle to the nucleus of an atom give that atom new properties? I can see how it changes it's mass, that's obvious... But how does it give that new atom different properties ...
61 views

Validity of topological thermodynamics?

I've been reading some material by R. Kiehn, developing a topological approach to non-equilibrium thermodynamics through Cartan forms, where the fundamental claim is that irreversible processes are ...
1k views

Why is the universe map shaped like an oval?

I understand that the Mollweide projection is used to show the map of the universe. Although I understand how this projection can be interesting for Earth where most populated (and of interest) ...
384 views

114 views

Classical Limit of the Quantum Harmonic Oscillator

The classical harmonic oscillator obeys an arcsine law in that the distribution of positions of the particle over a single time cycle is proportional to $\frac{1}{\sqrt{A^2-x^2}}$, $A$ being the ...
61 views

Import of Celestial Effects on Satellite Radio Interference

Some internet (among other) infrastructure comprises satellites, which beam communications in radio frequencies. These satellites, to ground observers, appear as very small solid angles in the sky. ...
83 views

permanent magnet energy field [duplicate]

Please explain to me this: What is the physical mechanism of the field and atraction force; in which way a force (electro, magnetic or gravity) is transmited between two objects? I will try to ...
112 views

Euler angle rotation - active/passive

I have a very simple problem, that I cannot wrap my head around and is hurting my brain. I have a very simple example of the problem, please consider the the figure below: In the first picture, you ...
162 views

Can this container withstand a vacuum? [closed]

I am putting together a piece of equipment that will involve a vacuum pump pulling up to 10 Torr / 13 Mbar.  I need to use a container for liquid within the equipment and have found a stainless steel ...
80 views

Why do we call a white led with high color temperature “cool”?

one can buy LED bulbs with defined color temperature. why cool white = many kelvins (= high temperature?) why warm white = few kelvins (= low temperature?)
39 views

Resistor color code extrapolation [closed]

I can't help wondering: what should the color stripes be on these?
24 views

Potential of 2 parallel plates

How can I write down a potential of 2 parallel plates (area $A$) with charge $+Q$, $-Q$ such that V(inf)=0 and V(in) is what I would expect, $Ed = Qd/A\epsilon_0$. Do I have to write a discontinuous ...
59 views

Traveling to Mars in 24 Days

I am trying to calculate an electromagnetic rail launch from the Moon but I need to know if humans can survive the launch. Please see the specs below. 150 miles of track Proposed final launch speed ...
60 views

Special Relativity - three body problem

I have a problem with solving three-body problem in special relativity. I know that in general this problem doesn't have good solution, but I have a specific case when it should be good answer. ...
86 views

Uniqueness of the equivalence class of inertial frames

Let us define an inertial frame as a frame of reference where the laws of physics take their usual form, as opposed to non intertial frames where one has to introduce pseudo-forces. We can further ...
64 views

Does the non electrostatic force moves charges in open circuit?

I would like to ask you a question i have about the non electrostatic force inside a emf device in open circuit situation. The following text is a text from Univeristy Physics ( Young and Freedman pg ...
125 views

Sakurai QM section 5.8

If anyone is familiar with Sakurai's book, specifically section 5.8 on energy shift and decay width, I am stuck and could use some help. I can't see how he derives 5.8.9 (in the revised edition). He ...
46 views

What makes red giants big? [duplicate]

I read some about red giants and so far I understand red giants become exhausted of burning hydrogen in the core, so then start hydrogen burning at shell and may or may not be burning helium in the ...
206 views

Coordinates for FLRW metric

In GR, coordinate are just a tool for us to describe the physics, they should be equivalent. However, in standard form of FLRW metric, it can be inferred that the universe is expanding, but we can do ...
159 views

Magnetic Wire Doesn't conduct Electricity

I recently bought a 22 and 30 gauge loop of magnetic wire from radio-shack. The loops of wire were colored differently (if this makes any difference) and on the package it noted how these wires were ...
27 views

How does a, halftone screen work?

Forever I've seen explainations that say a halftone printing image is made by photographing through a screen. But I have yet to see explained how that does the trick. Apparently the screen is placed ...
44 views

What's the relation between the type (Gender) of a balloon and its internal pressure

I'm working on a project about balloons and I need to know the relation between the gender of the balloon and its internal pressure. As far as I know, there are some parameters such as " Elasticity of ...
92 views

Can liquid contain information?

Is there any principle in physics that would allow liquid to contain some kind of information - could we, for example, in theory, use a glass of water to save information? For example digital photo ...
31 views

A question on tangential and centripetal accelerations?

What is the proof that the component of acceleration perpendicular to motion for all motion is $v^2/r$, where r is the radius of curvature? Also, what is the proof that the component of acceleration ...
521 views

What is potential energy truly?

I have a problematic question for which I have been unable to attain a satisfactory answer. What is potential energy truly? - I have read about how potential energy can be seen as the "highering" ...
47 views

Mullins effect in the elastic material

I was thinking on a experimental question, but I couldn't get the answer: How can we measure how the Mullins effect influences in the pressure inside a balloon? (I mean that, if there is a formula, ...
15 views

Transmitting to and from low earth orbit?

I'm a hobbyist and I'm currently thinking about building a Cubesat. I'm currently designing PCBs, casing, etc. I was wondering what variables are involved with sending data to and from 250km - 350km ...
468 views

Why does my apple not weigh 500 tons?

Related to this question: What is potential energy truly? $E=mc^2$ - energy equals mass. So, if an object has gravitational potential energy relative to another object, it should have additional mass ...
160 views

What is the advantage of using exponential function over trigonometric function in analyzing waves?

A.P.French in his book Vibrations and Waves writes: . . . Why should the exponential function be such an important contribution to the analysis of vibrations? The prime reason is the special ...
62 views

Do unmeasured particles function the same as when measured?

If there are particles that we are uncertain of are in a state of superposition, do they still function as they would when they are measured? For instance say there is a mechanical clock, and the ...
54 views

In order for the occurence of beat, why is it compulsory that $|{\omega_2 - \omega_1}| \ll \omega_1 + \omega_2$?

As A.P.French in Vibrations and Waves writes, The beating effect is most easily analyzed if we consider the addition of two SHM's of equal amplitude:  \mathbf{x_1} = \mathrm{A} \cos{\omega_1 .t} ...
64 views

Does wearing jewelry increase chance of static electricity

I am the only one in my office repeatedly subject to static stock. Does wearing silver jewelry increase my chance of getting a shock?
110 views

Phase shift in back-reflection generated at the mating point of two fibers

If you have light traveling from glass to air at normal incidence, e.g., in an optical fiber with the endface open, the Fresnel reflection coefficient would roughly be $R = |(1.5-1)/(1.5+1)|^2 = 0.04$ ...
28 views

Problem on bending plates in Newtonian Mechanics?

I am reading a book on interesting physics problems and demonstrations. One of the problems in the section on buildings, structures and equilibrium talks about a plate with one side attached to the ...
63 views

General two state system with general pertubation

I am trying to solve this two-level system with time independent perturbation problem Consider an atomic system with only two stationary states $|1\rangle$ and $|2\rangle$ , of respective energies ...
3k views

Stretch length of horizontal and vertical springs

If the spring in Figure A is stretched a distance d, how far will the spring in Figure B stretch? The spring constants are the same. The answer is "by half". I don't get it, to me it's the same.
32 views

Is the buoyant force on an object is the reaction force?

Is the buoyant force on an object is the reaction force for the force exerted by the objects on the fluid (newtons third law)? Or there are two sets of action reaction force? (objects force and ...
8k views

What is Convective acceleration of flow velocity?

I know that $\frac {dv}{dt}=a$ is acceleration, but: what is convective acceleration of a flow velocity? what is difference between $(v\cdot \nabla) v$ and $v\cdot (\nabla v)$, ?
245 views

Can two single particles interfere with each other?

Groups of particles can interfere with one another; In the double slit experiment when measuring single photons at the screen each one arrives at the screen in a random manner and they only show the ...
101 views

How can we measure chirality in experiments?

Chirality is a concept quite different from helicity. These two concepts only happen to have the same numerical value for massless particles. I understand that we can measure helicity, but how can we ...
138 views

Relation between sound waves and air molecules

The following was written in my book When sound waves travel in air, air molecules do not move. When wind blows,air molecules move. This produces variation in velocity of sound waves. The first ...