25 votes
Accepted

Aren't all objects luminous in a sense?

Black bodies are in equilibrium with their surroundings - they absorb radiation from their surroundings and then re-emit it. Luminous bodies have internal energy sources, i.e., there is energy ...
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9 votes

Aren't all objects luminous in a sense?

Yes, all objects emit radiation. But without other considerations, I would interpret "nonluminous" to simply mean that it isn't emitting visible light. My cat is quite warm, but I would use ...
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  • 33.6k
7 votes
Accepted

Difference between point force and force

Newtons law do not only work with point forces, It works with all forces associated with a vector field. Finding the force to a non point object requires integration. The most standard way a force is ...
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  • 3,652
6 votes

Aren't all objects luminous in a sense?

As you say, all matter is radiating, even black holes! In principle, the phrase "nonluminous objects" should be qualified by what part of the spectrum they can be considered nonluminous and ...
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3 votes

Difference between point force and force

An object, or a body, consists of particles. You can think of body as a collection of particles. Each particle has its mass and its coordinates in respect to origin of chosen coordinate system. Body ...
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3 votes

Difference between point force and force

In most problems in high school we assume the body as rigid,so it doesn't make any difference if the force is point load or a distributed load. But if you see in practice the point load will cause ...
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  • 31
2 votes

Why kinetic energy is called kinetic energy and not potential even though it has a potential to do work?

I mean 'kinetic energy' has also got the potential to do work, then why it's called kinetic energy? Because kinetic energy (KE) and potential energy (PE) are the two possible different forms of all ...
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2 votes
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What is an eigensystem? Could you provide a simple example?

Suppose we have a vector space. Since you're asking in the Physics SE an obvious example would be a Hilbert space, though there are lots of other such examples e.g. the normal modes of an oscillating ...
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1 vote
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Unable to make sense of - Heat, a form of energy

However, the textbooks also refer to heat, sometimes, as a form of energy, which doesn't make sense to me. Heat is one of the methods of transferring energy, how can it be a form of energy? You are ...
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1 vote
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What is $B(N)$ crystal structure? What does this nomenclature stand for

The Strukturbericht designations are one of several categorizations of crystal structures, going back to the early 1900s. "A" compounds are one element, with A1 being fcc, A2 is bcc, and A3 ...
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1 vote
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Ordinarily continuous function of the wave function

Griffiths is appealing to the semantic meaning: ordinarily=usually. For OP's other questions, in particular the bootstrap equation (2.127), see also e.g. my related Phys.SE answer here.
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1 vote

Terminology: does this situation correspond to an anisotropic but linear dielectric?

Yes, I would call this situation a linear dielectric: From Electrostatic Fields in Matter: Materials in which the induced polarization is proportional to the electric field are called linear ...
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1 vote

What is the Kepler problem, position as a function of time, or radius as a function of angle?

The Kepler problem (at least as applied to orbital mechanics) is to determine where an object is in its orbit and what its orbital velocity is as a function of time. It is not to determine $r$ as a ...
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  • 110k
1 vote

Why kinetic energy is called kinetic energy and not potential even though it has a potential to do work?

Kinetic energy is manifested in the form of movement. Potential energy is not manifested, that's why its called potential. For example, a body at height h from the ground has a gravitational potential ...
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1 vote

Why kinetic energy is called kinetic energy and not potential even though it has a potential to do work?

"Potential" is All energy, it has the potential to do work, Kinetic is energy applied energy of it's motion.
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1 vote

Why kinetic energy is called kinetic energy and not potential even though it has a potential to do work?

Potential energy describes the interaction, while kinetic energy is the property that describes itself
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  • 11
1 vote

How are the Bloch equations non-linear?

First, let me note that the equations given in the OP are not the full Bloch equations, which usually include the relaxation terms with characteristic times $T_1$ and $T_2$ for the longitudinal and ...
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1 vote
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How are the Bloch equations non-linear?

The non linearities arise when you consider the feedback loop. The magnetic moment can generate a field of its own. $\mathbf{B}$ will no longer be the externally applied field, but will rather depend ...
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