New answers tagged

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The spring constant is best thought of not as a single number to be measured, but as a relationship between two quantities: force and distance. As one quantity changes, so does the other. So, just as averaging multiple measurements can yield a more accurate result, measuring multiple points in a relationship can yield a more accurate $k$. The analog of ...


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You can use any position in the pendulum cycle to measure its period, but there are good reasons why using the mean position is likely to give you a more accurate answer than using an extreme position. However, note that if you are timing the period by measuring the interval between appearances of the bob at its mean position, then it must be going through ...


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Consecutive appearances at any given point in the cycle will all have the same phase. You don't need zero phase angle, just a constant one. The phase angle is changing at a constant rate, but the only way to determine it is to measure the distance and time together and calculate it from that. So we are back to measuring time accurately. This is best done in ...


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What you are describing is the diffraction pattern from a single slit as described in How can a single slit diffraction produce an interference pattern? The intensity as a function of angle is given by: $$ I(\theta) = I_0 ~ \mathrm{sinc}^2 \left(\frac{d\pi\sin\theta}{\lambda}\right) $$ where $d$ is the slit width and $\lambda$ is the wavelength of the light. ...


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The experiment of Michelson shows that the speed of light can not be c+v or c- v. First your misconception : traveling with c+v and c-v the same distance gives not the mean v of c. Imagin you start at your house and drive in your car with 100km/h. after 10 km you stop, and return very slow with 1km/h, so you need 1/10 h with the car and 10 h on foot, you ...


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With regard to your first question, I think there is a misconception. Photons move at a constant speed (c) and cannot be accelerated in a vacuum no matter how much momentum is applied to its emitter (see Einstein's Train). As counterintuitive as it may seem, light is always emitted at the same speed in a vacuum no matter how much acceleration the emitter is ...


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First of all: I do not know how well you can properly estimate the energy of detector the size of yours, but I guess that you would have very large uncertainties. But I can try to answer the first part of your question, how do you get the total energy of an event for a detetor array. You can read in detail about the energy reconstruction of a large array ...


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Suppose you prepare identical particles in an identical free state. That is, they have the same spread in space. You send them in opposite directions. If you make position measurements on the particles on one side after a time that is much shorter than the measurements that you make on the particles on the opposite side, you'll see that the spreading in ...


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The water flow through the holes will initially stop after the cup is dropped for the reasons given in the @DavidWhite answer. As the cup speeds up, however, Bernoulli forces will start to pull the water out through the holes. At first these forces will be counteracted by surface tension but eventually the Bernoulli force will win and water will resume ...


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Water flow through holes in the cup depends on pressure drop through the holes. That pressure drop is the difference between the water pressure on the bottom of the cup and atmospheric pressure. The pressure on the bottom of the cup before the cup is dropped is $P=\rho g h$, where $h$ is the height of the water in the cup. When the cup is in free fall, ...


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Theoretically, this is possible (as are a lot of things, as it turns out). However, there are a few issues with determining something like this experimentally. Free particles are hard to come by. Although particles can be close to free (i.e. relatively little force is acting on them), truly free particles are rare (if they exist). We can't measure a ...


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If I understand your setup and question, the following may be an approach. Assuming the figure below captures the basics of the marble on a track, we can consider the following. At the top of the ramp, the potential energy is at a maximum and as the marble rolls down the track, the energy gets transferred to a combination of translational kinetic energy and ...


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From the abstract of The Status and Prospects of the Muon g−2 Experiment at Fermilab: There stands a greater than 3 standard deviations discrepancy between the Brookhaven measurement of $a_μ$ and the theoretical value predicted using the Standard Model. The Fermilab experiment seeks to either resolve or confirm this discrepancy, which is suggestive of new ...


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I would suspect the What is the largest number of bosons placed in a BEC would be the largest vat of liquid below boiling point 4He. I think 4He must be in the ground state to be a non boiling liquid and this is effectively a BEC.


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I’m not an expert in biophysics and have never worked with molecules but I’ll try to answer your question in terms of experiments with electrons and photons. On the one hand, there are many physical processes in nature by means of which one can generate superposition states given some initial state prior to such processes to which one can initiate the system....


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Coupling efficiency and coupling loss are essentially two different ways to describe the same thing. The coupling efficiency is the portion of the incoming light in the first fiber that is coupled to the desired mode(s) in the second fiber. $$\eta = \frac{P_{\rm out}}{P_{\rm in}}$$ Coupling efficiency is usually expressed as a numerical value (as shown above)...


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You seem to be asking whether there are equivalence-principle tests for long-range non-Newtonian gravity, but not tests for long-range non-Newtonian gravity which are independent of composition. (Set aside for the moment the detail that general relativity is a well-tested non-Newtonian theory of gravity; we're asking here about new interactions in the weak-...


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In your favorite electromagnetism text, there is a set of exercises proving that a $1/r$ potential for a point charge leads to a $\ln r$ potential ($1/r$ field) for an infinite line charge, and to a linear potential (constant field) for an infinite plane charge. In the cases of a finite line charge or a finite plans charge, a good textbook (or a good ...


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Nothing at all. But if you think that this means that you can set $\delta q = 0$, then no, you can't. The formula for computing the error in $S$ through quadrature assumes that $S$ depends on the variables $q$ and $w$ with uncertainties $\delta q$ and $\delta w$ being independent of each other. Thus, the formula gets values for $\delta q$ and $\delta w$ and ...


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There is no light or force being applied to the cube If the cube is in our universe, there is always the force of gravity of the nearest neighbors, within Newtonian gravity. That was the way General Relativity was established as necessary to describe the solar system. There were outer planets that did not fit the orbital solutions expected , and this made ...


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From your description, it seems that your detection system is operating in a nonlinear region. Nonlinearities in the detection system will complicate things, so making sure the detector is operating in its linear range will be very important. If the detection is linear, separation of the ambient and signal beam effects should be fairly straightforward. A ...


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The psd method basically moves the signal from d.c. to some other frequency, and then is sensitive to noise at that other frequency. Therefore you pick a frequency where the noise is small. Many noise sources decrease with frequency, so often one picks as high a frequency as your detector and de-modulation stage (usually a lock-in amplifier) can handle.


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Bodies radiate EM waves as a function of its temperature. So, if the cube is above 0 K, its presence can theoretically be detected.


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As for measuring the rebound height, I would suggest you use a camera (make sure the camera is fixed, not hand held). Drop the ball alongside a wall with a ruler or other tape measure fixed on the wall. You may get errors due to parallax so place the camera relative to the ball and ruler so as to minimise errors caused by parallax. Note the height of the ...


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In 2011, the OPERA experiment claimed to have detected neutrinos that traveled faster than the speed of light. Einstein's theory of relativity doesn't allow particles with mass to travel faster than the speed of light, so this experiment violated his theory of relativity. What happened subsequently, is described in this truly excellent summary, which gives a ...


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I'm guessing a direct measurement is one you would read directly from your measuring instrument, like a weight on a scale or the size of an object read from a tape measure. An indirect measurement might require a calculation, like the mass of a planet from the orbital period of a moon.


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"Do physicists just use the word standard deviation to refer to uncertainty?" Often we assume that results of our measurements are normal distributed (we can argue that, if we don't know the reason for the deviation from the "real" value, then it is most likely due to many factors and if you have many arbitrarily distributed factors ...


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You cannot prove a theory wrong, because a theory is like a world-view. Claiming that a theory can be proven wrong is like claiming that the concept of "color" or "speed" is wrong. Theories can of course be inconsistent, but they would then be rejected instantly. Now, physics theories are still connected to "real life" with what ...


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A microwave oven generates its radiation via a magnetron which is based on a resonant cavity. Unless the cavity has been damaged in some way, there is not really any way for it to change its output frequency. In response to the idea that a plate heats up instead of the food, in fact there are some materials commonly used for plates that readily absorb ...


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My question would be, what happens in the scientific community if one experiment proves it wrong We have already seen what happens in this circumstance by looking at what happened to Newtonian gravity. First, well before the development of general relativity there were observations that did not fit with Newtonian gravity. For example, Uranus’ orbit did not ...


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Words like "proven" and "wrong" have to be used carefully in this context. It is more meaningful to talk about "accuracy" and "limits". If an experiment was conducted tomorrow that contradicted general relativity it would by no means make general relativity a useless theory, nor would we get rid of it. The purpose of ...


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Measurements that use the same method can be assumed to have the same systematic error, affecting all measurements equally. So you can, for example, take an average value of these measurements or discuss the consistency of different measurements without knowing the systematic error. However, it is not possible to compare measurements made with different ...


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If you assume the uncertainties are Gaussian distributed, then 1 is 1000 sigma away from 0 +/- 0.001. To a first approximation, you can ignore the much smaller uncertainty on 1. You can use the complementary error function to determine the probability of finding a value at $n$ sigma away from the mean value (for Gaussian uncertainties). For example, \begin{...


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Indeed, an inertial observer can ascribe himself a state of "proper rest" or "proper motion". However, in SR an observer rarely founds himself in a "moving frame", an observer is usually "at rest" in his own frame. Two spatially separated and Einstein - synchronized clocks of his "rest frame" measure longer ...


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Let's assume two identical objects being in relative motion wrt each other. Let's also assume they got their motion in a symmetrical way (by accelerating from each other with the same acceleration)). Their clocks are synchronized at the start. If one of the two accelerates and decelerates to enter the other object, there will be a difference in time on the ...


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A magnetic field is a form of energy. Energy is required to form a permanent magnet by, e.g., aligning the spins of electrons in a material. That energy is stored in the resulting macroscopic magnetic field. The same is true of an electric field: energy is stored in the macroscopic electric field when positive and negative electric charges are separated, e....


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You cannot magnetize something without bringing it into the magnetic field but that takes work and the amount of work you have done while keeping the magnetic field unchanged is the energy acquired by the newly magnetized body. If the source of the magnetic field is a permanent magnet whose magnetization does not change while moving another magnetizable body ...


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A SG apparatus measures the spin projection of electrons in a given axis (the one where the magnetic field is applied). For example, a SG in the z direction measures the probability of finding electons with spins in the up and down states in the z axis. Once your electrons pass through a SG device, their wave function collapse because of the measurement, ...


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Thibado "published" about this idea three years ago https://researchfrontiers.uark.edu/good-vibrations/ https://youtu.be/wrleMqm3HiU He now added complications (diodes etc) but that won't help. The system with mechanical noise makes it a bit more complicated but not really different from a resistor with thermal noise. It is like trying to get ...


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The interpretation is almost certainly wrong. A graphene film cannot "ripple" due to a static, spatially uniform temperature. It can only mechanically deform in response to a changing temperature or a temperature gradient. If all the calculations are done properly, the graphene film device will be determined to be a heat engine whose performance ...


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A simple analogy based on the same physics. Have you ever bounced pebbles on water? If not see this video . Here is an explanation for the pebble, from which the angle and speed is the basic for the skipping meteorites. At high speeds and small angles the effective density of matter the meteorite scatters off is high enough to be like the water surface ...


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An object, initially in an eliptical orbit, has a radial (due to gravity) acceleration. If there was no atmosphere it would continue following that orbit, unless if it intercept the earth surface. When the object enters in the atmosphere, the acceleration changes due to drag and bouyance. $\mathbf a = \mathbf g + \mathbf a_d + \mathbf a_b$ $\mathbf a_b = -\...


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I found a good paper here titled Distinguishing quark and gluon jets at the LHC from CERN's website that answers your question. The introduction states "Partons emitted from hard scattering process at the LHC form, due to QCD confinement and hadronization process, hadronic jets, which can be revealed with tracking and calorimeter systems. As known from ...


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I think the problem arrives in the way the diagram on wikipedia shows the negative charges to sit on the wand and its metal sphere. While the large metal sphere is being positively charged, (actually it is having its negative charge stripped), these negative charged are carried by the belt towards the grounded earth, and thus 'disappear'. However once the ...


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[My] domes are all far from the VDG. In most design of VDG, I saw that one dome is placed encapsulating the top roller. But in my design, both domes are far apart connected with some cabling. That won't work. The fact that the upper dome encloses the apparatus that takes the charge off of the belt is the most important part of the design. It's literally ...


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This answer is incomplete, as I'm no expert, but it may be of some help. The idea of having the top roller assembly surrounded by the dome is that the charges that build up on the outside of the dome will not give rise to an electric field inside the dome, so charges arriving on the belt are not inhibited from leaving via the top comb. I'm not at all sure ...


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