The result of sampling the property of a system

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14 views

Thermistor calibration - estimation of number of reference temperature points needed

A thermistor changes resistance with the temperature in a non-linear way and follows the exponential Arrhenius equation. Two reference points, ice slush water and boiling water, are used for ...
0
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0answers
20 views

Measurement of two qubits in a tensor product space

I understand that if we have two qubits, say $\Psi \in \mathcal{H}_1 \bigotimes \mathcal{H}_2$ where Alice has the first qubit, and she makes a measurement and ends up with the state $\phi \in ...
2
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1answer
97 views

Problem on Einstein - de Haas experiment

I am a Physics student (4th year) and I'm trying to study the Einstein - de Haas effect in laboratory. That is what I got: a suspended Iron cylinder with about 5 cm height and a radius of 0.8 cm is ...
-2
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0answers
26 views

Which units are affected if we double the unit of length/velocity or force? [on hold]

If the unit of length: $m$, velocity: $v$, and force: $N$ is doubled, which of the following options is correct? (changes in other unit) unit of time is doubled unit of mass is doubled unit of ...
2
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1answer
22 views

How to measure the fineness of a textile fibre by diameter and fibre length?

I measured the diameter (um) and the fibre length (cm) of different (loose) textile fibres and have an average. Now there must be a relation between these two factors that gives an idea of the ...
0
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1answer
83 views

What is the difference between zero background radiation and field background radiation in Nuclear Physics measurements?

Can someone please explain the difference between these two terms (Zero Background Radiation and Field Background Radiation) used in radiometric prospecting measurements?
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0answers
50 views

measuring distances

We measure distances using half of the time of flight of light, 'a la Einstein'. What is the geometrical shape of the surface that is the locus of the points that are at a definite distance of an ...
0
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1answer
55 views

Do subatomic particles have dimensions?

We know atoms are mostly "made" out of empty space, so the nucleus and all the subatomic particle are very small in compared to the magnitude of the atoms. We also know that atoms are incredibly ...
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0answers
15 views

How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with $V(t)=V_0\cos{(\omega t)}$.
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1answer
40 views

Good way to compute the force of a hammer blow?

What is a good and easy way to compute and/or measure the force of a hammer blow, not using any fancy or specialized equipment? If the hammer is swung by hand through an arc, it is not obvious to me ...
11
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3answers
482 views

If time standard clocks and any memories about the time standard are destroyed, can we recover the time standard again?

Assume the time standard clocks and any memories about the time standard are destroyed. Can we recover the time standard again exactly? Recovering the time standard again means we can determine the ...
1
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5answers
99 views

The nature of measurement

Does the measurement of the particle change it's physical state? Or does it only seem to do that? Ex. if a particle was measured before the slits, would we see an interference pattern, or a particle ...
2
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2answers
128 views

How to use an accelerometer to correctly quantify the magnitude of vibrations

Consider the following setup: An accelerometer is placed inside a helicopter, measuring $g$ values along three axes $(x,y,z)$ every $10~\text{ms}$ (100 times a second), during a helicopter flight. ...
4
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2answers
632 views

Do the copper connectors we used in measuring the resistance of a wire contribute to the said measurement?

We measured the resistance of a wire by setting the multimeter to ohmmeter mode and connected the ends of the ohmmeter to the ends of the wire; and we also calculated the theoretical value using a ...
4
votes
2answers
124 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 ...
0
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1answer
326 views

Is it possible to use induction ampermeter to measure power consumption of electric water heater and dryer?

I hope this practical question is not OT and not too trivial for this forum. I am renting an apartment in a duplex with a shared water heater and dryer. Turns out, both water heater and the dryer are ...
21
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4answers
3k views

If the LHC-calculated mass of the Higgs is wrong, how long will it take to determine this with confidence? [closed]

After I watched "Particle Fever"--the movie about Large Hadron Collider (LHC) and the successful identification of the Higgs boson--I became a bit concerned with that team's handling of various ...
3
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4answers
120 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
votes
1answer
134 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 ...
14
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2answers
5k views

Home experiments to measure the RPM of a pedestal fan without special equipment?

Is it possible to determine to an approximate degree, the revolutions per minute of a fan, for example a pedesal fan pictured below, without using some electronic/mechanical measuring device? One ...
6
votes
1answer
295 views

How do bathroom scales measure body fat percent?

My bathroom scale has 2 metal strips each for a foot and the producer claims that it can measure body fat percent. There is a warning in the manual, that if I have heart problems (I guess pacemaker), ...
1
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0answers
32 views

What technologies are available to measure distance? [closed]

I'm a programmer, I really lack of physics knowledge, I'm trying to make some basic design for a distance measuring simple system, for a social project I'd take as hobby. Basically I would have many ...
1
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3answers
106 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
45 views

Distinguishing between prepared and unprepared states Stern-Gerlach experiment

$ \newcommand{\bra}[1]{\left\langle #1 \right|} \newcommand{\ket}[1]{\left| #1 \right\rangle} \newcommand{\braket}[2]{\left\langle #1 \middle| #2 \right\rangle}$I have a problem and am confused as to ...
2
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0answers
62 views

Molecular structure correction factor in Mass Flow Controller

This question concerns device called Mass Flow Controller (or Mass Flow Meter). For a video explaining the principle: see https://www.youtube.com/watch?v=G62ma2IFh9o These devices are factory ...
1
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0answers
49 views

Justifying the use of real numbers for measuring length

I am not sure if this is the most appropriate place to post this but here goes nothing: Assume we were trying to come up with system of numbers $S$ to model our intuition of length. We want $S$ to ...
0
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1answer
45 views

Light speed measured by observing Jupiter moons [duplicate]

The famous discovery that the light has speed measures the times of the immersion and emergence of Io, one of Jupiter's moons. However, I still can't comprehend this. Even when the Earth is further ...
19
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1answer
2k views

How did Rømer measure the speed of light by observing Jupiter's moons, centuries ago?

I am interested in the practical method and I like to discover if it is cheap enough to be done as an experiment in a high school.
0
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1answer
41 views

How much time between measurements do you have in order to make the same measurement on a particle?

As I understand it, you can make a measurement on a particle and if you quickly carry out a second measurement you will get the same outcome as the prior measurement. If this is the case, how much ...
4
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10answers
2k 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 ...
7
votes
5answers
937 views

Proving and demonstrating vacuum in container without breaking it

Let there be a hollow container made of glass or some other transparent material, roughly the size and shape of an apple. Let the walls be of sufficient thickness for the container to be safely ...
0
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2answers
57 views

How to calculate the error in measurments of derived quantities knowing the error in basic quantities?

I wonder how to calculate error of a derived quantity $z$ knowing the error of all quantities that $z$ depends on say $x$ and $y$. For example: Suppose I want to calculate the speed of a body ...
4
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2answers
71 views

Examples of (classical) measurements that are not independent?

What are some simple examples of measurements that are not statistically independent, i.e. with nonzero covariance? I'm looking for real examples that might reasonably come up in an undergraduate ...
1
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1answer
122 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 ...
6
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1answer
2k views

Why does an infrared thermometer display very low temperature when being directed to the outer air?

I'm toying with an infrared thermometer - one which you point onto an object, press the button and it instantly measures the temperature by estimating the infrared radiation from the object. It shows ...
0
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0answers
25 views

What is the limit of directly detecting a resonance?

Some resonances are extremely short-lived. With a lifetime of $10^{-23}$ seconds, they would travel just about the size of the proton ($10^{-15}$ m) even if they traveled at the speed of ...
1
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0answers
65 views

Query about the proof why non-orthogonal states cannot be reliably distinguished

I have a query regarding the proof given in the book by Nielsen and Chuang on why two non-orthogonal states cannot be perfectly distinguished. The proof is given on page 87 of the 10th edition; here ...
4
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3answers
87 views

Can liquid contain information?

Is there any principle in physics that would allow liquid to contain some kind of information - could we, for example, in theory, use a glass of water to save information? For example digital photo ...
1
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1answer
62 views

What are the methods of experimentally measuring the observables in quantum mechanics?

Perhaps due to the limited number of textbooks on quantum mechanics I have consulted, I have seen presented the fundamental principles related to observables, but have never seen a somewhat systematic ...
1
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4answers
141 views

How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
1
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1answer
40 views

How is the curvature of space measured on earth scale?

How do we measure the curvature of space due to earths gravity since we can't dig a hole through the centre of the earth and measure the actual diameter of earth which is slightly different (1.8cm) ...
2
votes
2answers
58 views

How does a supersonic flight speedometer work? [closed]

I'm sure today they can use GPS and radar, but I was pondering the queation when I saw a film clip of a vintage analog dial labeled in mach number. I'm supposing that the usual way of measuring the ...
0
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0answers
8 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 ...
0
votes
1answer
26 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 ...
1
vote
1answer
49 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 ...
0
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0answers
21 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 ...
3
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1answer
21 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 ...
1
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1answer
146 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 ...
0
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3answers
88 views

Accelerometer validation trace

I am attempting to validate an accelerometer. I have a triaxial accelerometer and placed it on a wheel which goes at various frequencies from 1 to 3 Hz. Am I right in thinking that I would expect the ...
0
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2answers
64 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 ...