Units are standards of measurement used for different types of quantities.
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1answer
174 views
$E=mc^2$ why is it $c^2$ and not just $c$?
Why is constant for the conversion of mass to energy square of the ligths speed? is it bedside it's the fastest real matter?
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1answer
464 views
Question Concerning Dimensional Analysis
In the first lecture of MIT's Classical Mechanics Professor Lewin talks about Dimensional Analysis.He talks about an apple being dropped from a certain height can be quantitatively expressed as the ...
1
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1answer
306 views
Converting Notes to Milliseconds
Given a note duration (whole, half, quarter, etc.), a tempo (in beats per minute), and a time signature, how long does that note last in milliseconds?
3
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1answer
1k views
How does the Fourier Transform invert units?
I don't really understand how units work under operations like derivation and integration. In particular, I am interested in understanding how the Fourier transform gives inverse units (i.e. time ...
2
votes
3answers
165 views
What widely recognized organizations set standards used by physics?
I recently answered a question about the meaning of the word "dimension" as used in physics. In that response, I provided the definition given in the International Vocabulary of Metrology (VIM) and ...
0
votes
1answer
480 views
Changing magnetic flux graph?
In regards to a graph of the changing magnetic flux in a generator such as this one:
a) The equation of the graph should be $\Phi = BA \cos \theta$. As $\theta=\omega t$ (angular velocity*time), ...
3
votes
3answers
223 views
Physical interpretation of describing mass in units of length
I'm working in Taylor and Wheeler's "Exploring Black Holes" and on p.2-14 they use two honorary constants: Newton's constant divided by the speed of light squared e.g. $G/c^2$ as a term to convert ...
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2answers
2k views
Unit for Impact Force
Forgive me if this is a newb question but I am not a trained scientist, much less a physicist. I'm just curious and would like to know if there's a unit to measure impact force.
I know the newton is ...
6
votes
5answers
876 views
Is anything actually 1 meter long (or 1kg of weight)?
I believe that no real objects are actually (exactly) 1 meter long, since for something to be 1.00000000... meters long, we would have to have the ability to measure with infinite precision. ...
13
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9answers
3k views
What is the logarithm of a kilometer? Is it a dimensionless number?
In log-plots a quantity is plotted on a logarithmic scale. This got me thinking about what the logarithm of a unit actually is.
Suppose I have something with length $L = 1 km$.
$\lg L = \lg km$
It ...
0
votes
3answers
146 views
units of measure
This question is rather historical one.
kilometres can be defined in metres, metres in centimetres, centimetres in millimetres.
There must be some elementary unit (like millimetre or smth.) which ...
4
votes
10answers
882 views
Addition of different physical quantities
We all know the "apples and oranges" rule which says that it's meaningless to add or subtract two different quantities like apples and oranges. But the same rule doesn't hold for the multiplication ...
4
votes
4answers
1k views
What exactly is a mole?
I have some trouble understanding exactly what a mole represents. As I understand, one unit mole is 1/12 of the mass of an atom of carbon-12 (thus it is the mass of one nucleon?). What is a mole, ...
6
votes
5answers
472 views
Whats the range of dimension exponents in the SI Units system?
I am working on a software library for Units of Measure. To represent dimensions, I need to know the required range of exponents for each of the seven base units (precisely, I need to know the ...
2
votes
2answers
487 views
Fundamental units
Is it right that all units in physics can be defined in terms of only mass, length and time?
Why is it so? Is there some principle that explains it or is it just observational fact?
8
votes
4answers
488 views
Simple Harmonic Motion - What are the units for $\omega_0$ ?
I'm trying to understand the units in:
$mx''+kx=0$
And the general solution is $x(t)=A \cos(\omega_0 t)+B \sin(\omega_0 t)$
Let $\omega_0 =\sqrt{\frac{k}{m}}$ - the unit for the spring constant $k$ ...
1
vote
1answer
135 views
Non-Dimentionalization of equations
I am trying to understand a paper in which they mention;
" We non-dimentionalize the problem hereafter by selecting mass, length and time units such that the fluid density
$\rho\equiv1$
the ...
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votes
3answers
271 views
Help getting the distance an object has moved
What is a distance an object went through at the speed of 14hm/min for 6 hours?
I am having problems with conversions.
First, I tried passing 14hm/min to m/s. I did it alright. But now I am unsure. ...
8
votes
3answers
548 views
Understanding counterintuitive units like s^2
One of the things I never understood but was too afraid to ask is this: how should I think of things like kg/s^2. What exactly is a square second? Square foot makes sense to me because I can see it, ...
14
votes
3answers
1k views
Fundamental question about dimensional analysis
Let me admit beforehand that this is quite possibly a very stupid question. I was also uncertain of where to post this question, as it doesn't fit cleanly into either physics or math stackexchange.
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