All Questions

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Importance of Powers of Velocity in Classical Mechanics

This is an incredibly naive question, but I am curious enough to ask anyways. Is there any general significance to calculated quantities that depend purely on general powers of the velocity of a ...
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Conductors and Uniqueness Theorem

I'm working with Griffiths Electrodynamics, and he introduces a uniqueness theorem: First Uniqueness Theorem: The potential $V$ in a volume $\Omega$ is uniquely determined if (a) the charge density ...
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Degree of freedom paradox for a rigid body

Suppose we consider a rigid body, which has $N$ particles. Then the number of degrees of freedom is $3N - (\mbox{# of constraints})$. As the distance between any two points in a rigid body is fixed, ...
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Can a string be so thin it's invisible, but still support a visible weight?

A spider web thread is very thin, yet it can support a spider. Given that the human eye visual acuity is finite, are there materials, natural or man-made, sufficiently thin that a string made from ...
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Fill and drain tank (same time) [on hold]

Consider an open tank with cross section area A, into which liquid can enter at the top through one pipe and leave at the base through another. If the liquid enters at the constant rate of a volume of ...
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How To Calculate A Meteor Impact

Exalted Physics Gods of the Internet. I am trying to add a dose of realism to a story I'm writing. Long story short: Basically imagine an invulnerable superman-like being that won't disintegrate at ...
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Quadratic versus other types of degrees of freedom

In my text book I have the following question and after thinking about this one for hours, I can't figure out what they're getting at: In Section 2.5* I quoted a theorem on the multiplicity of any ...
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How does electrostatic force affect electronic devices?

How does electrostatic force generated by two seperate plates having opposite charges affect electronic devices? I know that magnetic fields have some harmful effects to electronic devices but I am ...
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Question on the negativity of the coefficient of restitution

I was trying to solve a Mechanics question on Momentum. Here is the question : Two small smooth spheres A and B have equal radii and have masses m and km respectively. They are moving in a ...
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On deriving the Schrödinger Equation

I do know that one can't actually derive any axiom, but here is my serious attempt to explain the Time Independent Schrödinger Equation with minimum preliminary knowledge. In the following $f$ is ...
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Is it possible to have rate of change of acceleration?

I know this may seem a weird question, but it always bothers me. My physics book (Resnick,Halliday,Walker), and also various sites never say anything beyond acceleration. But when a moving body is ...
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Dielectric constant of water

I need the dielectric constant of water from $10^{-2}$ Hz to $10^4$ Hz. As stupid as it may seem, I cannot find much info. I've googled for days. All I can find is close to GHz. And the only info ...
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Mapping Issues with Unbounded Operators

Consider the operator-valued generalized function $\phi^{(k)}_{l}:=\phi^{(k)}_{l}$ on space-time $\mathcal{M}$. Now, smooth the operator-valued generalized function with test function $f(x)$ ...
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Homopolar motor and Lorentz force

My second grader thought making a homopolar motor for her science experiment would be fun. And, it was. Now I am trying to explain how it works and the Lorentz force. Please help me by giving me a ...
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Final temperature of an air parcel

How would one find the final temperature of an air parcel ascending adiabatically in the atmosphere? Like which formula would you use? I used the equation of state for dry air to find the initial ...
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Using Maximum Principle to see conductor is equipotential

This is a problem from electrostatics, but I'm trying to understand it in terms of harmonic functions. Let $B\subset\mathbb{R^3}$ be a conductor. It can be shown that the electric potential ...
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Calculation of the partition function for a classical 2D gas lying on the surface of a sphere of constant radius $R$

I'm kind of confused with this system. My first question is. Is the Hamiltonian of one particle of this gas the following? ...
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If an unsaturated air parcel ascends adiabatically in the atmosphere with an initial temperature, would the final temperature of the air parcel, when it reaches it's destination, be the same at the ...
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Is the plane wave model always valid in reflection and transmission?

my question is related to another one I asked, but I foolishly made that question about several things (experiment, computation, theory) at once so it was confused. I was talking to my boss about ...
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Energy usage in different reference frames

Imagine a moving object at constant speed (like a car). This object is, then, accelerated for a brief moment. In different reference frames (at rest and moving along with the object), the variation of ...
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HW Question: Force of a Car on a Truck

Here is another homework question that is confusing me... A 1000 kg car pushes a 2000 kg truck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push ...
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Application of Kirchhoff's laws in circuits with inductors

As we know,the Kirchhoff circuit laws are applicable for conservative electric fields. Now it is applicable for circuits where inductors are present but the field there is not conservative. So how ...
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why is the focal length of a convex mirror negative?

According to the Cartesian sign convention, the focal length should be positive since the convex mirror forms a virtual image to the right of mirror (positive direction) when light comes from left. ...
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Maximum friction force for a wheel to be able to roll

The wheel with mass $M$ and radius $R$ below is free in space (it is not on the ground). A torque $\tau$ is applied to it through an engine. A horizontal force $F = \frac{\tau}{R}$ is also applied to ...
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Indicate if objects after collision will stick

Is it possible to indicate if objects after collision will stick together knowing their properties(materials,hardness,etc)?
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How is graphene a 2D substance?

How is graphene a 2D substance? It has length, width and some thickness to it, else it would be invisible. Why is it considered a 2D substance?
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Beta plus decay [duplicate]

I think I understand beta minus decay: A nucleon loses mass and this mass is converted into an electron and an electron anti-neutrino. Correct? (I imagine there might be some kinetic energy too but ...
What is the difference between the projection of a moment, about a point $O$ on an axis $l$, along that axis $l$ vs. the projection of a moment, about a point $D$ not on that axis $l$, along that ...