The measurement tag has no wiki summary.
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1answer
38 views
How many measurements should be done? [closed]
I am measuring time of a computer operation. The operation should run roughly same time each time I measure it. How many times should I measure it to get good average and standard deviation?
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1answer
34 views
Measurement uncertainty of the quantity, that is function of two others quantities
I'm trying to compute uncertainty for the density of the ball.
I measured its radius 6 times, so I was able to compute the stastistical uncertainty (we call it uncertainty type A, I don't know, if ...
4
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3answers
115 views
Precision of Coulomb's law
Up to which precision has the coulomb law proven to be true?
I.e. if you have two electrons in a vacuum chamber, 5 meters appart, have the third order terms been ruled out? Are there any theoretical ...
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2answers
109 views
Magnitude refers to number or number with units?
This question is about terminology for physical quantities.
When we talk about magnitude (while talking about scalars and vectors) do we refer to just number or Number along with units?
example: If ...
5
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3answers
1k views
Rough, easy DIY method of measuring magnetic field strength
How to easily, using standard DIY equipment measure the strength of magnetic field generated by a permanent magnet?
Narrowing down the "loose language" of the above:
strength of magnetic field: ...
5
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2answers
76 views
What is known about the Magnetic North Pole's location before 1800?
I was recently startled to find that the Earth's North Magnetic Pole is moving at upwards of 40 km per year, with an additional ~80 km daily elliptical drift about its mean position due to variations ...
2
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1answer
47 views
Is this the correct way to I combine multiple interdependant pressure readings?
I want to measure the density in different layers of a suspension. To do this I want to place pressure sensors at different heights. Let's assume that the sensors are not by orders of magnitude more ...
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2answers
78 views
Is there any phenomenon in physics which is sensitive to irrational numbers?
We can measure only rational numbers by our scale. Here is an example where irrational numbers does makes sense. If so then this question may have some theoretical importance. Is irrational numbers ...
6
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3answers
512 views
Measuring the spin of a single electron
Is it possible to measure the spin of a single electron? What papers have been published on answering this question? Would the measurement require a super sensitive SQUID, Superconductive Quantum ...
3
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0answers
112 views
projective measurement & POVM
Let us consider the following completely positive map $\mathcal{B}(\mathbb{C}^n)\ni\rho\mapsto L\rho L^\dagger$, where $L\in\mathcal{B}(\mathbb{C}^n)$ is any arbitrary operator (and can have rank ...
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2answers
88 views
How can we detect a black hole? [duplicate]
If black holes are phenomena of very high density (gravitational singularities) which don't emit radiation how can we detect them so far away from us where so much other radiation can hide the black ...
4
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1answer
32 views
Is there a naturally occuring sound pressure level reference?
There are lots of devices that purport to measure the absolute value of sound pressure levels. Here is an example, here's another, there's also this iPhone App. Putting such devices side-by-side in ...
4
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2answers
77 views
Mean of a measurement on periodic data: what is the use of the inverse of correlation length?
Correlation and autocorrelation is something that in my Bachelor's programme in physics has been somewhat overlooked, so I'm in trouble understanding their use in this paper (The prisoner’s dilemma on ...
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5answers
220 views
Are Uncertainties in Measurements Important?
In the first lecture of MIT's Classical Mechanics Prof. Lewin highlights the importance of uncertainties in measurements by quoting "Any measurements, without the knowledge of uncertainty is ...
4
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1answer
131 views
On the Aharonov-Bohm effect, and the reality of the classical fields
As far as I can check, the Aharonov-Bohm effect is not -- contrary to what is claimed in the historical paper -- a demonstration that the vector potential $A$ has an intrinsic existence in quantum ...
7
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0answers
103 views
Why is the Planck length the shortest measurable length? [duplicate]
I quote from the Wikipedia article on Planck length:
According to the generalized uncertainty principle, the Planck length
is in principle, within a factor of order unity, the shortest
...
8
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3answers
523 views
How hot is the water in the pot?
Question: How hot is the water in the pot? More precisely speaking, how can I get a temperature of the water as a function of time a priori?
Background & My attempt: Recently I started spend ...
2
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2answers
44 views
Asymmetric uncertainties
Inspired by these two question on tex.SX
Asymmetrical tolerancing
Asymmetric uncertainties with siunitx package
I'd like to ask for a nice explanation for these kind of uncertainties, like ...
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3answers
145 views
What truly is mass, and is there a direct way to measure it?
We know a mass of an object of one kilogram as an object that weighs W = mg = 9.8 N and we reference it to that, (when it should as a fundamental parameter describe weight not the opposite). But if we ...
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0answers
130 views
How do I measure the temperature of a tiny water droplet?
How do I accurately (+/- 0.1 degrees Celsius or better) measure the temperature of a small (5 to 50 microliter) water droplet without noticeably affecting its temperature?
The mass of a thermistor or ...
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0answers
35 views
About the resolution/$\sqrt{12}$ uncertainty
Suppose you want to measure a (real-valued) quantity with an apparatus which will return as a result of the measurement the closest integer to the true value of the quantity.
Then, a common use is to ...
1
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0answers
29 views
where to find sample fluid stirring data?
I want to find some force data for fluid stirring. Originally I intended to record the data using my force sensor, but it doesn't have the resolution to read stirring force for Newtonian fluid.
...
0
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1answer
44 views
Velocity of measurement
As per to Heisenberg uncertainty we will not be able to calculate the position and momentum at same instant because by the time we calculate the next of the one, it changes (i.e.) the changes are very ...
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1answer
75 views
Uncertainty in Acceleration given the uncertainty in position
I had a motion detector record the position of a dynamics cart and automatically plot Position vs Time and Velocity vs Time plots in Logger Pro on the computer. If the instrument uncertainty in ...
1
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1answer
67 views
Experimental perspective in understanding the Heisenberg Uncertainty Principle
I need to confirm whether or not I understand Heisenberg Uncertainty Principle. So the crucial thing is that you need an "ensemble" of measurements:
$$\delta x \delta p \ge \frac{\hbar}{2}.$$
If I ...
8
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1answer
343 views
Why is carbon dating limit only 40,000 years?
For an example, when they tried to get the carbon dating for presence of Aboriginal people in Australia they get to the number 40,000. But it could be much earlier. Why is that 40,000 years limit for ...
3
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2answers
1k views
Measuring acceleration of earth due to its fall around the sun
Every orbiting of a satellite around a mass is nothing else but a constant fall - and therefore acceleration - towards this mass. In a way it is a "falling around" that mass.
My question Is it ...
2
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2answers
87 views
Decomposing light into frequency spectrum
Light hits a charge coupled element. The wavelength of the light somehow is translated into a color picture. Where can I learn about methods (algorithms) to decompose light hitting a CCD into ...
7
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1answer
261 views
How to measure a solid-solid surface energy?
Many techniques exist to measure the surface energy between a liquid and a liquid or a liquid and a gas (see e.g. the wiki page).
Methods to measure the surface energy between a solid and a fluid are ...
5
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1answer
134 views
Practical method to weigh human limbs with common household items?
What methods could be used to determine (or estimate within a reasonable margin of error) the mass of a living human's limbs, short of cutting them off? And more interestingly, how can this be done ...
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1answer
205 views
What's the difference between 'least count' and 'smallest division'?
I'm wondering the difference between the 'least count' and the 'smallest division' of an instrument.
Can you explain that for me, plz?
1
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1answer
144 views
Photometer: measured Irradiance L converted to photon rate
I am conducting an experiment in which the power meter reading of $410\,nm$ narrow bandpass stimulus is noted to be 30 $\frac{\mu W}{cm^2}$ at a distance of 1 inch away from the light source.
I wish ...
3
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1answer
134 views
Quantum computing problem
Suppose that a qubit is in the state $|\varphi\rangle=a|0\rangle+\sqrt{1-a^2}|1\rangle$, where $a\in[-1,1]$.
If we first perform a standard basis measurement on this qubit and then perform a
...
5
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1answer
99 views
Measuring acceleration of a bus using water between two sheets of glass
I was riding a bus one day and noticed that the double windows had some water between them. As the bus accelerated, the water collected to the sides, first forming a trapezoid and then a right ...
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4answers
196 views
Does measuring destroy entanglement
Before measuring a quantum particle(photon) it exists in a superposition state, once we observe(measure) it, it settles in one of the possible states(destroying superposition).
For entangled ...
2
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1answer
49 views
Multimeter has a resistance
If a multimeter has a resistance (1M ohm, say) when measuring voltages how do I take that into account in my error?
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4answers
483 views
How to describe a well defined “zero moment” in time
Suppose you have to specify the moment in time when a given event occurred, a "zero time". The record must be accurate to the minute, and be obtainable even after thousands of years. All the measures ...
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2answers
84 views
Electron mass changes with website
When particles mass can be changed by changing the website, then how to calculate with confidence?
For example:
Google: electron mass = 9.10938 188 × 10$^-31$ kilograms
Wikipedia: electron mass
...
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1answer
93 views
Does photon have size measurement because of its particle nature
Does photon have size measurement because of its particle nature like electron's 3.86*10^-13m etc..
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3answers
155 views
Setting up a local-coordinate system in space-time using only a single clock and light beams
I have a question to ask about the operationalist view of space-time. I am a mathematician who happens to be interested in physics, so if anyone thinks that my question is a silly or vague one, please ...
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11answers
749 views
Is it possible for a physical object to have a irrational length?
Suppose I have a caliper that is infinitely precise. Also suppose that this caliper returns not a number, but rather whether the precise length is rational or irrational.
If I were to use this ...
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4answers
443 views
How does a train, airplane measure its speed?
I always get the doubt about this. I know that a bike measures its speed based on the motion of its front wheel. So what is the case with train? Is it same principle? Then what about an airplane? Is ...
3
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1answer
110 views
Finding radius of Earth through observation of Sun's motion
The question I'm about to pose is from a physics book I had recently bought. Since I am very interested in physics I am quite keen in understanding how this question can be solved. Before I present ...
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0answers
40 views
Experimental data for gas flow through pipelines
Maybe some of you could point a good source of experimental data of gas flow through pipelines? What I need is a very simple flow of some gases through some diameter simple linear pipeline. A graph of ...
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0answers
300 views
How to calculate uncertainties of a natural exponential function?
(I apologize if this should be posted in mathematics, however I chose to post it here as it's technically about physics)
I conducted an experiment in which position of items were shifted on an ...
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1answer
70 views
Measuring the quantum state of light
A clarification please
The following scheme to measure linear polarization states (a single polarizing beam splitter and two photo counters) orientation (as $arctan \sqrt{\frac{v}{h}}$) of coherent ...
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0answers
86 views
Measurement in Quantum mechanics
I have got a quantum conservative system whose Hamiltonian is $H$. I consider an selfandjoint operator $O$ whose eigenvalues and eigenvectors are: $$O|\psi _{n}\rangle = \lambda _{n}|\psi ...
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0answers
28 views
What methods exist for us to measure the position and momentum of atoms that make up molecules?
In reference to this paper, http://iopscience.iop.org/1355-5111/8/1/014, we are able to localize atoms using homodyne measurement. Would it be too naive to consider we can measure the position of ...
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1answer
59 views
When are leap seconds added in various time zones?
I understand that technically when a leap second is added, it is added after midnight UTC, but I'm unclear how the addition is handled in other timezones. For precise reckoning of course (e.g. ...
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3answers
207 views
experimental technique for measuring temperature of an ant
I am taking a course on thermodynamics. I have a question from my text(halliday & resnick,physics-1). They asked me to measure temperature of an ant or an insect or a small body,like a small ...
