The result of sampling the property of a system

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14 views

Tight bounds between maximum weight and precision

Scales are rated according to their precision and maximum load -- attributes which seem to be universally close to one another (within about 3x10^4 grams). Eg, a scale that can measure up to a ...
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1answer
32 views

Measuring mass zero G [closed]

I work for a company that produces (among other things) a microbalance that can measure mass/weight from around 100ng to 100mg ie it is accurate over 6 orders of magnitude. However, this relies on ...
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1answer
50 views

Is it possible to determine which combination of three degenerate states an atom is in, not destroying the state?

Suppose we have somehow determined that an atom's outer shell electron is in a $p$ state (i.e. with $l=1$). For example, waited enough for a cold boron atom to almost certainly come into electronic ...
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0answers
24 views

PT100 calibration

I have also asked this on the electronics group, but it is equally relevant to physics of temperature mearurement If I take (say) a class B PT100 sensor with a stated absolute accuracy of +/- 0.3 deg ...
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1answer
28 views

Scale Factor on Error

I was gathering some data from the particle data group website and for many results it gives a value, an uncertainty and then a scale factor for the uncertainty. For instance, at here, where it gives ...
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1answer
167 views

Significant Figures in Physics

A string has linear density $10.0 \cdot 10^{-3} \, \mbox{kg/m}$ and is kept under a tension of 100 N. A sinusoidal transverse wave, with a wavelength of 0.30 m, is traveling in the positive direction ...
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1answer
82 views

Why is the voltage output equal to the voltage drop?

I have a very basic question about measurement of voltage output on some simple circuits. Considering the circuits of the figure: Supposing one wants to measure the voltage output $V_2$, on the ...
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1answer
50 views

Where are the negligible and infinite resistances, respectively, of the ideal am- and voltmeter?

Consider the picture below. An ammeter is shown to the left, a voltmeter to the right. They consist of a d'Arsonval galvanometer, which is a coil (with a pointer attached) that can rotate in a ...
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1answer
134 views

Measurement of cross section

When we measure the cross section of an interaction what is it that we actually measure in a real experiment? I know what cross section is and how to derive an expression for a given process but I ...
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61 views

A method/device for measuring angles, as an experiment?

What's the best device for measuring angles, as an experiment for a fundamental physics lab at the university level? The first experiment in our fundamental physics lab is "Measuring & Measurement ...
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0answers
48 views

The amplitude of oscillations in sound waves

How can the amplitude of molecules displacement be measured in a sound wave? How can the amplitude of the pressure fluctuation be measured in a sound wave? What are the difference between these two ...
2
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1answer
43 views

How are specific volumes accurately measured experimentally?

In every thermodynamics textbook there are tables containing the specific volume of various fluids at different temperatures and pressures. My question is, how is this data obtained experimentally? ...
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2answers
40 views

What probability distribution the detection counts have?

As far as I know in quantum mechanics each particle have a separate normalized wave function that can be used to calculate that the particle can be found somewhere. Or more practically to determine ...
2
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50 views

Are there limits to human/devices perception?

As far as i know, measurement devices present measurements based on something that affects the device's particles, for instance, forces, heat, tension, voltage... My question is, given that every ...
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2answers
71 views

Experimentally, what categorizes a measurement as corresponding to a certain observable?

I want to write a computer program. The input to the program is: A description of an experimental device (for instance a Stern-Gerlach apparatus, or a laser and a polarizer) What the experimenter ...
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0answers
56 views

Propagation of uncertainty - proof that it is minimal

I am not really sure if this is the right SE community for this question, but, I swear, I haven't found any better. The problem is as follows: we have n distance sensors placed around a quickly ...
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1answer
47 views

Why does the rule for multiplication/division take into consideration the no. of significant figures?

I've learned that the rule for multiplication, when taking into account the significant figures, is as follows: The final result should retain as many significant figures as there are in the original ...
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3answers
114 views

Does every interaction of quantum objects introduce backaction?

The motivation of this question is the following experiment: Assume you have quantum mechanical oscillator, e.g. a particle in a potential $V(q_x)\propto q_x^2$. Now the position of the particle ...
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1answer
40 views

Uncertainty of approximately sinusoidal voltage measurement

Say one is interested in measuring the mean value an approximately sinusoidal voltage with an instrument that has an accuracy of 0.01 V, according to its spec sheet. 10 periods of the oscillation have ...
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1answer
149 views

How does one figure out how fast water is moving through a water intake on a dam?

Say the dam is Hoover dam for example. The intake is where the water flows in to turn the turbines that generate electricity. I want to know if there is an equation that describes the speed of the ...
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7answers
452 views

Can a ultracentrifuge be used to test general relativity?

With today's ultracentrifuge technology, they can spin so fast that the sample can be subjected to accelerations of up to 2 millions Gs. That is equivalent to two solar masses. Has someone tried to ...
3
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3answers
171 views

How to theoretically define a concrete operation to perform in order to measure the length of an object?

EDIT: Some answerers pointed out that the title of this question is in contrast with what is actually been asked in the body of the question, so I changed the title accordingly. The original title was ...
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2answers
46 views

Non-random observations (regarding physical quantity)?

Are there completely deterministic observations? More detailed: Talking about an observations process for which of the following sentences would you vote: Version 1 (always random): "These ...
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2answers
148 views

What is the experiment used to actually observe the position of the electron in the H atom?

Prior to observation, the electron can be found anywhere (from inside the nucleus to the ends of the universe), but once its position is determined the answer is precise (albeit its momentum is not ...
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5answers
235 views

How is anything *not* ultimately a position measurement?

Consider measuring the momentum of an electron. You pass it through some kind of electromagnetic field, it strikes a photodetector (e.g. a CCD), and you back-calculate out the momentum of the ...
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1answer
83 views

The Force Required To Move An Object Which Has Unequal Mass Distribution

Suppose I have an object, let's say a stick which is of length, let's say 1 meters. I have most of the mass of the stick concentrated on one side of the stick (the center of mass). Now, if I move the ...
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3answers
115 views

Repeating a measurement vs uncertainty

The wikipedia says on measurement in quantum mechanics that: Repeating the same measurement without any evolution of the quantum state will lead to the same result. On the other hand, doesn't ...
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0answers
8 views

Extracting times of hits from a composite detector response

I have a detector that registers a sequence of "hits" over a period of time. Each hit produces a signal that has the approximate form ...
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2answers
139 views

No length contraction in thought experiment with co-moving measuring stick

Suppose a person standing on a platform were to observe and measure the length of a train passing by. Instead of the usual approach involving a clock and knowing the speed of the train, the person ...
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0answers
38 views

Maximum error of number of observations within several certain intervals – Accuracy of variable is known

I have carried out a series of measurements of different thermal comfort parameters from which I have calculated another variable called PMV. My data set consists of hourly measurements (and ...
2
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1answer
86 views

Uniqueness of representing POVM using projective measurement

$\newcommand\tr{\operatorname{tr}} \newcommand\ket[1]{\lvert#1\rangle} \newcommand\bra[1]{\langle#1\rvert} $[Skip to the conjecture for a self-contained mathematical formulation of the question.] ...
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0answers
59 views

For thermal mass flow measurement technologies is it necessary to measure gas pressure to determine volumetric flow rate?

Mass flow readings from thermal mass flow measurement technologies often provide output readings in volumetric units (e.g. standard liters per minute). Mathematically I can derive the volumetric flow ...
4
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2answers
81 views

Does measuring the air temperature near a 21 lane asphalt highway impact measurements?

The official temperature in Sydney is measured at the Sydney Observatory. This is located near the city side of the Sydney Harbour Bridge - which is a major highway. My question is Does ...
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1answer
365 views

Frictionless Cart on a Ramp (Experimental Design Question)

Question: Why is the calculated value for our final velocity higher than our predicted value? Since our prediction neglected air resistance and friction, shouldn't the velocity for the actual cart ...
3
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1answer
82 views

How do we perform transverse measurements in a two level system?

In quantum mechanics any two level system can be mapped onto effective spin variables. If the system is defined by two energy levels, $|E_1\rangle$ and $|E_2\rangle$, the Hamiltonian is $$ H = ...
3
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4answers
152 views

How can I measure the speed of a figure skater's spin?

My daughter is a figure skater and needs to measure how fast she is spinning before she loses her position. This is a science project for 7th grade. I have looked for devices to possibly measure her ...
3
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2answers
198 views

How can you accurately determine your own mass?

I'm trying to figure out whether it is possible for an individual to accurately determine his/her own mass, to within 100g, using equipment that is readily accessible or can be purchased at a ...
2
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2answers
134 views

How should I quote errors when measurements are asymetrically clustered?

Suppose five people measure the length of a stick and report the following values 4.90cm 4.92cm 4.93cm 4.94cm 4.94cm In high school science we are told that in ...
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0answers
101 views

Is there a way to measure the energy stored in a twisted rubber band?

I am building an energy storage device using rubber bands. It contains 24 bands which are twisted by a set of gears. I would like to measure (or predict) the amount of energy that the device can ...
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2answers
76 views

can one measure energy to a finite accuracy?

Can one measure energy to a finite accuracy in bounded amount of time? I don't know much about QM, but someone told me that the energy-time uncertainty principle says that it would take infinite ...
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2answers
63 views

U.S. Standard Atmosphere

My textbook states that "Ideally, we would like to have measurements of pressure versus altitude over the specific range for the specific conditions (temperature, reference pressure) for which the ...
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1answer
132 views

Thought Experiment: Force on magnets in a Stern Gerlach Experiment

Background: In the SG experiment, an inhomogenous magnetic field affects a force on particles passing between two magnets. "Measurement" takes place when a screen is placed on one end, blocking one ...
9
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1answer
127 views

Is it possible to determine whether distant galaxies are gravitationally bound

In a previous question, one issue was related to the potential energy of cosmic structures. This raised in particular the question of whether these structures are gravitationally bound. If you ...
2
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1answer
81 views

Measuring more accurately the distance of remote galaxies

From what I read in Wikipedia, the velocity of a Galaxy has two components: one is due to Hubble's law for cosmic expansion, and the other is the peculiar velocity of the galaxy. Since the peculiar ...
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2answers
381 views

What is the spin of an electron along the x-axis?

I know that an electron or any other particle for that matter, has a measured spin which is either up or down. This spin is along the z-axis. But what if we do not measure it along the z-axis and do ...
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0answers
54 views

How many measurements of a physical quantity should you do to get a representative value / distribution? [closed]

When we measure a physical quantity multiple times, we can calculate several values which should help us understand the whole measurement better: Standard deviation, variance, median, average, and so ...
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1answer
58 views

How and under what principle are measurements made at quantum level? [closed]

There's a lot of news about amazing quantum phenomena, but even without the expert knowledge I would still like to know how it is done and think about the possibility of errors in measurements. How, ...
2
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1answer
79 views

What was a second in the early universe?

I have read some popsci articles and documentaries about the early universe and they often explain how various features of the universe came about and at what time. For example hydrogen atoms came ...
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3answers
157 views

Scalable quantum computation vs Uncertainty Principle

tl;dr. : If we want the result of a quantum computation to have scalable more bits, we will need inner measurements to have scalable precision, if we already know the result of the computation (from a ...
2
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3answers
168 views

Measuring position and momentum at the same time?

In a non-relativistic quantum mechanical system in an infinite potential well. I try to measure the energy and the position of the system simultaneously. Since, the respective operators do commute ...