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13 votes
Accepted

Is there a name for the number of '9's in numbers such as 0.999 (where it would be 3)?

I've heard 'nines' used frequently in quoting the purity of a material, and it turns out that this is a standard, though informal term. Wikipedia has this to say: "Nines are an informal ...
user34722's user avatar
  • 2,503
3 votes
Accepted

What is the tangential component of any vector?

Yes. If the velocity vector is $\mathbf{v}$ the kinetic energy is $K=(1/2)m|\mathbf{v}|^2$ - it only depends on the magnitude of the vector, not is direction. So a force that is tangential to the ...
Anders Sandberg's user avatar
3 votes
Accepted

Is the set of possible elementary particle types equal to the set of all combinations of their properties?

You seem to be asking whether the properties you've listed allows one to uniquely identify a particle. The answer is no, because: There are combinations of these properties that don't exists. For ...
Michael Seifert's user avatar
2 votes

What is the tangential component of any vector?

What is the tangential component of any vector? a force component that is parallel to the velocity component? Or is something lacking in my understanding of the word tangential? Yes, the tangential ...
ryang's user avatar
  • 804
2 votes

What is the tangential component of any vector?

That is correct. The work done by some force over a given distance is $$W=\vec F\cdot \vec s$$ where $\vec s$ is a vector describing the displacement over which the force happend and $\cdot$ denotes ...
AccidentalTaylorExpansion's user avatar
2 votes

What is the tangential component of any vector?

A force causes an acceleration (Newton’s second law $\mathbf{F}=m\mathbf{a}$). Next, acceleration is by definition the rate of change of velocity $\mathbf{a}:=\frac{d\mathbf{v}}{dt}$. Speed is by ...
peek-a-boo's user avatar
  • 6,605
2 votes

How to call ellipse packing structures?

I'm not aware of any specific terminology, but it makes sense to me to consider both of these as hexagonal configurations of hard-core ellipses. Reversing your compression operation, they can be ...
Anyon's user avatar
  • 2,709
2 votes

Terminology for time derivative of speed (not velocity)

I want the time derivative of speed. This is a useful concept, because it matches the colloquial sense of the word ‘acceleration’; if this quantity is positive then an object is speeding up (...
ryang's user avatar
  • 804
1 vote

Is there a scalar acceleration?

just as distance is some scalar different from the magnitude of displacement, You mean that distance travelled does not equal the magnitude of displacement. This is true. If I walk to the store and ...
ryang's user avatar
  • 804
1 vote

What type of variable would you classify $a, b, c$ etc shown in the picture? Would I just call them random, insignificant real values?

a, b, and c might be a measured values where the measurement process isn't perfect. The measurements are tied to some physical features of the universe, but they are not exactly the right numbers. If ...
mmesser314's user avatar

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