for questions about design, process, data, or analysis of experiments and observations.

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1answer
26 views

Systematic+Random Uncertainty for velocity measurement

I have a question regarding systematic and random uncertainties. I have to measure the mean value of a velocity measurement in flow field at a point. I've recorded say 1000 samples in time, which I ...
46
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3answers
2k views

Why are LIGO's beam tubes so wide?

Gravitational wave detectors and particle accelerators have at least one thing in common -- they require long vacuum tubes through which a narrow beam is fired (a laser in the gravitational wave case, ...
1
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1answer
34 views

Can vernier scale ratio be less than 1?

I came across a question (See Image) that states about two vernier scales The first vernier scale is the top-most figure in the image: It has 10 vernier scale division equal to 9 main scale division ...
1
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1answer
27 views

Heat loss by radiation reference

In our lab practice, we measured the rate of heat loss of a copper plate in atmospheric pressure and the rate of heat loss of the same plate in high vacuum ($\sim 10^5 torr$). So all I could find for ...
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0answers
12 views

Transverse momentum [duplicate]

I'm having an introduction on detector systems in particle physics. The sources I read constantly talk about the measurement of "transverse momentum". However, I cannot find a definition of what is ...
5
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1answer
51 views

Optical Retroreflectors: How Are the Faces So Accurately Righted?

This question is about Optical Retroreflectors (corner cubes) and how the extreme precision in their manufacturing is achieved. I suspect there is interesting basic physics involved, which is why the ...
1
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1answer
39 views

Why surface tension behaves so differently?

When a needle (or any other object) floats on water, its acting upwards balancing the gravity. But when an object (or may be a needle suspended in water) submerged in water, it acts downwards. ...
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0answers
27 views

Four point probe method under liquid nitrogen

I was trying to measure the resistivity of the YBCO superconductor (but not like a resistivity- T diagram, but only at liquid nitrogen boiling point), so I needed to put the sample in thermal contact ...
0
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0answers
16 views

The distribution of net charge in the Millikan oil drop experiment?

What is the distribution? Of course it depends on the concrete setup. But, what is the typical value? The concern is that, if the distribution is peaked at, say 1000, it would be very difficult ...
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2answers
55 views

Lamina Pendulum Experiment help

I've been tasked with researching ways to find the gravitational acceleration g and its uncertainty together with the moment of inertia and and the moment of inertia's uncertainty. I have figured out ...
0
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0answers
21 views

LIGO Gravitational Wave Discovery and Gravitons [duplicate]

Now that gravitational waves have been detected, how hard will it be to detect a graviton? Will the equipment have to be more sensitive or are the difficulties more complicated than that?
3
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2answers
71 views

Best way of calculating average acceleration in lab experiments

I am doing a lab experiment that works as follows. An object moves along the $x$ axis with an initial acceleration and then moves with a pretty constant velocity that may slightly vary within $20\%$ (...
0
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0answers
31 views

What is space charge Capacitance of diode?

Most of the books say that $p$-type and $n$-type materials of diode act as parallel plates of space charge capacitance were as the depletion charges (uncovered) act as dielectric. Then why do these ...
0
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1answer
21 views

Why characteristics graph of Geiger Muller Counter always goes up?

The characteristics graph of Geiger Muller Counter always keeps going up and does not drop down . It may remain constant over an interval but does not drop down on the graph scale. Why it does not ...
0
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0answers
20 views

Classification of experimentally-determined physics laws? [duplicate]

Has anyone classified (or attempted to classify) all the experimentally-determined laws of physics, such as with a simple diagram or even in a full-length book?
0
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0answers
19 views

Statistics: combining independent observables for the same quantity, how to check independence

Let's assume we have a set of observations $\{x_i\}$ and that I have a physical models aimed to describe the observations, and that this model has a parameter $y$. Let's assume that I have two ...
0
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1answer
46 views

special relativity mirror experiment

There's an experiment in special relativity that involves a light source and a mirror, both placed in a moving object. It is used to derive the time dilation equation. I'm having serious doubts about ...
-1
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1answer
25 views

how to check if the experimental performance of the oscillation amplitudes follows the predicted trend? [closed]

once I got my set of amplitudes how can I compare experimental amplitudes with damped harmonic motion? I know that $F = -kx + mg -(C_1 + C_2 |v|)v $ supposing c2 = 0 and cos = 1 $x(t) = Ae^{-\...
0
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2answers
46 views

Interference or something beyond?

I have an experiment with He-Ne laser in my practical syllabus. In curiosity I took a photo of the incoming radiation directly from the laser with my mobile camera. Some strange pattern is observed. ...
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0answers
40 views

Estimate heating wires temperature

Im design a power supply to work with heating wires and one of the task is to estimate the temperature of the bare wire for a given current or power consumption. I've tried to measure the ...
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2answers
164 views

Why is it that the refrigerators (ice houses) from long ago can't be reconstructed in modern times? [closed]

A Long time ago (a couple of hundreds of years), people could make a refrigerator by applying a certain procedure with pieces of ice, harvested in winter, and other stuff. The ice hadn´t molten at the ...
0
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2answers
36 views

Measuring potential

I apologize if the question below has been asked -- I could not find an answer. A charged conductor some distance above ground generates an electric field and corresponding potential profile. How ...
0
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1answer
32 views

Why is the standard deviation the error on the singular measurement?

I'm a beginner with the study in data analysis in Physics. I'm trying to understand the meaning, in the field of experimental Physics, of the standard deviation $\sigma$ of a series of data. There ...
6
votes
1answer
273 views

Why is the gravitational constant so difficult to measure?

The gravitational constant seems to be very low precision. For example, in the Wikipedia article recent measurements are given as having the significands of 6.67 and 6.69, a difference of 2 parts in ...
3
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0answers
41 views

What experiments confirmed Poynting's Theorem?

Actually, I have two related questions. The fist is the above question. The second is, what experiments confirmed that $\varepsilon_0\left(\frac{E^2}{2} + c^2 \frac{B^2}{2}\right)$ is the ...
0
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1answer
46 views

Propagation error for a third grade equation

I am trying to find the value for the roots$\pm$error for a set of experimental data. The function that fit the best is $$\epsilon(t)=a+bt+ct^2+dt^3.$$ Which is the best way to calculate the roots $\...
3
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1answer
46 views

Are asymptotic states in scattering experiments really momentum eigenstates?

In a typical collider experiment, two particles, generally in approximate momentum eigenstates at $t=-\infty$, are collided with each other and we measure the probability of finding particular ...
0
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0answers
31 views

I need results or to conduct a simple experiment for a dynamics problem involving the range of a projectile launched from a pendulum

I have created a model to show how the maximum range of a projectile varies with respect to the velocity and angle of when the object is launched from a swing. I now need to compare these results ...
3
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0answers
36 views

Why would oscillation of a gas column inhibit rather than promote mixing?

Many years ago I helped to support an experiment conducted in Japan which investigated the effects of high frequency oscillation ventilation (HFOV) on the mixing and distribution of gas into the lungs....
0
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0answers
17 views

Springs and Cantilevers - how linear and repeatable are they under deformation?

I know you guys only deal with the ideal, but in practice how linear and repeatable is the response of a spring or cantilever when deformed under a test mass?
2
votes
1answer
55 views

What is the minimum sample sizes to show the error bar in an experiment?

In scientific experiment, people often try to show an error bar based on the standard deviation around a mean (average) value. My question is twofold: How to estimate the minimum but adequate ...
3
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1answer
46 views

Does the human body have a measurable gravitational field?

I am researching communication other than speech or vision. The human body emits radiation in the form of heat; As the body has mass, will it have a gravitational field?
0
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0answers
8 views

Optimum “fur” dimensions for absorbing ultrasound at a given wavelength?

By "fur" I mean an array of bendable fibres aligned vertically on a substrate. The ultrasound hits it at an oblique angle. Is there a spacing that will provide optimum absorption? A basic thought ...
4
votes
4answers
107 views

Intensity fluctuations at the output of a single mode fiber coupled to a He Ne laser

I have coupled a Thorlabs HNL050L-EC - HeNe, 632.8 nm, 5 mW, Polarized Laser to a 2 meter long single mode fiber patch chord using a Thorlabs F230-FC-B aspheric lens. While I am certainly able to ...
1
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0answers
44 views

Lab experiment: hysteresis disappears, reappears and then disappears again. How?

In my college laboratory we were assigned an experiment to measure the hysteresis curves of a certain ferromagnetic material at different temperatures. Sounds simple, right? Well, the block of Monel ...
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0answers
48 views

Speed of the Coulomb Field Measured To Be “Infinite”

The paper "Measuring Propagation Speed of Coulomb Fields" by R. de Sangro et al points out that: ...the Lienard-Weichert retarded potential leads to the same formula as the one obtained assuming ...
0
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1answer
17 views

Mach-Zehnder probabilities

Where can I find the computations of probabilities for Mach-Zehnder experiments, say at the undergraduate level? For example I'm thinking of the type of experiments described at the beginning of David ...
2
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0answers
36 views

Any method to determine the gravitational constant $G$ from observations in cosmological scale?

By the observations in cosmological scale, I mean observations by astrophysicists like motions of quasars in far distance from us, relative motions of our galaxy to others, etc. I know the famous ...
0
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1answer
41 views

Reverse osmosis Water desalination

Is it feasible to submerge a reverse osmosis system in the sea in order to use the increasing pressure to push through the membrane and as the salt was removed would the lighter water rise on its own?
1
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0answers
25 views

what is the effect of temperature on the resistance of a photoconductor?

As we know, for a photo conductor resistance tends to decrease with increase in irradiance, but with greater irradiance comes greater temperature. Also we know, photo conductors are semiconductors,...
0
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2answers
27 views

Probability of Millikan's drop gaining or losing charge during the experiment

I performed Millikan's experiment with latex drops. I did not get the "step graph" that I wanted (though the precision of the experiment was really bad as seen in the figure). My first drop is ...
0
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1answer
60 views

Coulomb law and photons

When we consider process like $e^- e^- \to e^- e^-$ in QED, we see that from exchanges of one photon (tree-level diagrams) one can obtain Coulomb's law, while loop-diagrams give quantum corrections ...
0
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0answers
27 views

What is the smallest practical milliKelvin temperature sensor or technique?

I need to track the temperature of a mass of less than 1 gram, and the two constraints are accuracy and mass of the attached sensor/circuitry (it must be less than 1.5g). Ideally it should be a non ...
0
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0answers
25 views

How does sound propagate through a mesh structure?

I am assuming that the material and holes are approximately the same dimensions and also similar to the wavelength of the sound. In my case, around 2mm. How does varying those dimensions affect the ...
0
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0answers
10 views

Change in Q factor on tuning external magnetic field in Electron spin resonance experiment

Does the Q factor of the cavity resonator show a dip at the resonant value of the external magnetic field while performing an ESR experiment?If so, what is the physical reason behind it?
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3answers
4k views

How can an electron fake a jet?

This is a question for experimentalists. I have seen in several ATLAS papers (see for example chapter 4 in arXiv:1602.09058, 6th paragraph), that after objects have been correctly identified, any jet ...
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1answer
52 views

I can get a heating strip - why can't I get a cooling strip?

A typical heating strip is a flexible silicone material containing a resistive heater. However, I would like the opposite - something I can wrap around my experiment and use in a similar way to the ...
0
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0answers
20 views

GEN3's 10nm-30nm Contiuum Radiation Measurements

What is the most likely explanation for the 10nm-30nm continuum radiation reported in "Validation of the Observation of Soft X-ray Continuum Radiation from Low-Energy Pinch Discharges in the Presence ...
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0answers
28 views

How is mass of observable universe calculated? [duplicate]

How is even mass of earth known ? How do we get to know them? Whilst I was studying about dark matter it was listed about 'mass of observable universe' and density and so on...so what is the procedure?...
1
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1answer
147 views

Difference between theoretical equations and empirical equations

Some equations are theoretical in the sense that they are derived from an underlying theory. Other equations are empirical in the sense that they were selected only because they fit experimental data ...