# All Questions

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### Potential Energy in soilds :: Why are different equations used for deriving lattice constants and for deriving the properties of phonons?

While deriving the equilibrium lattice constants we use expressions for potential like lenard-jones potential which have 6th and 12th order terms or madelung energy for ionic crystals . While ...
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### What is the particle, rest, and kenetic energy of a beryllium nucleus?

A beryllium nucleus has mass 6.8e-27 kg. If its speed || is 0.988c (that is, ||/c = 0.988), what are the following values? Particle Rest Kinetic My problem is that the normal formulas for the ...
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### Can mass be directly measured without measuring its weight?

From Wikipedia, http://en.wikipedia.org/wiki/Mass Inertial mass measures an object's resistance to being accelerated by a force (represented by the relationship F=ma). Active gravitational ...
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### Why do we use kilograms instead of newtons to measure weight in everyday life?

What was the reason to use kilograms to measure weight (e.g. body weight, market vegetables etc.) instead of using newtons?
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### What is the physical interpretation of this quantity?

For the second order ODE governing the position of a projectile subject to air resistance $$m\frac{d^2x}{dt^2} +k\frac{dx}{dt}+mg=0 \quad k>0, \> x(0)=0, \> x'(0)=V>0$$ a ...
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### What is the future of complexity theory in black-hole physics and string theory?

I found the recent work by Hayden and Harlow and Susskind very fascinating. I have also heard talks by Scott Aaronson about this emerging connection. In particular this idea of understanding ...
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### Can you pull and also grind a material through a length of cylinder? [on hold]

I want to take plant matter for instance, and instead of splitting up the grinding phase and feeding through a tube phase (using a screw inside the cylinder), I'd like to combine them into one. So ...
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### What experiment disproved single fluid theory of electricity?

I just can't understand how history of electricity goes on. What experiment disproved Benjamin Franklin's fluid theory of electricity?
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### Induced emf in a circular conducting wheel

Consider a conducting wheel with $N \in \mathbb{N}$ spokes which is completely in a homogenous magnetic field $\vec{B}$ perpendicular to the wheel plane. ...
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### projectile motion angles [on hold]

A boy wishes to throw a ball through a house via two small openings, one in the front and the other in the back window being directly behind the first. If the boy stands at a distance of 5m in front ...
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### Non-invasive inspection technique [on hold]

I am looking for a way to inspect a metal canister that is approximately 30-50 m above ground from ground level. The canister is made of Alumimnum/steel and is made of two parts and is sealed so that ...
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### Pdf of particles in phase space

I am from a non-physics background and hence have difficulty in grasping the concepts some of which I need to apply in signal processing. Link1 and Link2 discuss about Liouville theorum and phase ...
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### Can we prove Conservation of Angular Momentum without assuming internal forces are central?

The only proof I've seen of Conservation of Angular Momentum assumes that the internal forces of the system act along the line joining particles i and j (i.e. - all internal forces are central.) Can ...