Measurement Definition and 1000 Threads

Hello, If I want to measure the concentricity of a cylinder with another, is it possible using a CMM? If yes, can you pl. explain me the procedure? I have read that concnetricity has to be measured based on the mid point of a diameter-line of a cylinder. This means, I have to measure the...

Hello PF members! First of all, let me start off my post by admitting that I have created a duplicate account. My original account was banned for a good reason. Now, I am studying physics. More specifically, I'm studying relativity. I trust that you all will help me understand what...

Hi, I have a question about how to interpret the state of an entangled photon H = horisontal, V = vertical polarization The global state is |Phi> = (|H>|V> + |V>|H>)/sqrt2. By density operator formalism: rho = |Phi><Phi| = (1/2) ( |H>|V><H|<V| + |H>|V><V|<H| + |V>|H><H|<V|...

Morning everyone, We know of some illusions in our everyday experience, such as an echo making us believe someone is talking back at us, or mirages in the desert, or mirrors making us think there are two symmetric objects when one is only the reflection of another. I was wondering about...

How can I measure the power associated with a vertical rotating shaft (similar to the shaft of a vertical axis wind turbine). power=Torque*angular velocity Angular velocity can be found by using tacho meter or spectroscope.. but i am confused how to measure the torque...

Do gyroscopes give the angular rates about its local axes or about a frame that is fixed and initially coincides with its local frame? I mean: would this sensor give the rate of change of the Euler's angles or the angular velocity ω (about the inertial frame)? One more question: I know that...

Im not sure if there are any implications to be made, but it struck me as interesting as what would happen if measurements of the same parameter were simultaneously made on each of two entangled particles? Can anyone speak to this perchance?

How do astronomers measure cosmic distance, say 7 billion light-years? http://www.space.com/17399-gamma-ray-photons-quantum-spacetime.html

First I am trying to find the theoretical flow rate but I am not able to get the answer because since diameter of the pipe is 0.03m throughout, when I sub into the formula: My A1/A2 will be 1, and 1-1 = 0. And I will get maths error whatever is divided by 0. Am I going in the wrong direction...

I always try to assume that pretty much anything I think of has been thought of before, so I am relatively sure that this is also not a new question. we base our current measurement systems on arbitrary lengths such as the meter or foot, etc. there are certain applications where we use...

what is differences between collapse,reduction, decoherence , weak projection and strong projection in quantum measurement theories?

hi I read this statement in site www.askamathematician.com and I couldn't understand it. is it possible to explain this? "if measurements A and B are taken enough apart, they will be “space-like separated” according to SR, meaning that neither event precedes the other. Some observers will...

Sorry if I'm in the wrong subforum. This is a rather simple and straightforward question, I hope. I'm doing a measurement that requires me to do a linear regression on data points to get a value of the slope. The slope is the value of the actual property that I am measuring. Assuming...

I want to ask a question regarding how spin state of an electron becomes entangled with the slit an electron travels through in the double slit experiment. So I understand that in the double slit experiment, we have two slits 1 and 2. We place a detector by slit 1 to measure whether or not...

Hi, I'm doing some research on developing a physics-based platform game and I want to see how the gameplay will feel if the environment and physics were made to scale as realistically as possible. Since one of the core features of a 2D platformer is jumping, I need some figures on how much...

Suppose we have x plates of wood of thickness (0.0150 \pm 0.0002) \text{ m} and we wish to stack them into a pile of height (1.000 \pm 0.001) \text{ m}. The number of plates x required is then x = \dfrac {1.000 \pm 0.001}{0.0150 \pm 0.0002} \, . How many plates will certainly fit in the...

why am I only getting 16v between both line phases coming into my service from the meter on a 240v single phase panel for a home

Homework Statement I am having a hard time understanding the length measurement in the problem. We went over this example in class and the length, L, was something I didn't realize until now. Question: A 6-ft-long steam pipe is made of A-36 steel with σ=40 ksi (yield stress). It is...

Hello, The quantum zeno effect is well understood and experimentally confirmed as regards polarization measurements (as discussed here). It's the quantum analogue of "the watched pot never boils" as it allows "continuous" measurement to inhibit certain state evolutions. Does the effect...

Hi! I found a few old threads lying around regarding this, such as this one, but I thought I'd start a new one asking the question in my own way. So here goes. Is the uncertainty described by the Uncertainty Principal a result of the fact that by measuring something we affect it, or a...

I'm having a gap in understanding the relation between them, and resolving my confusion is really appreciated. For example, the Hamiltonian operator, why do we call its eigenvalues energies? how do we actually measure it in the laboratory, quantum mechanically? And maybe I need a better...

We define time by the rate at which physical processes (i.e. clocks) tick. With atoms for example we can define time by their energy transition rates such as in atomic clocks. But, what before atoms existed? Current cosmology theories make statements such as that '0.5 seconds after the Big...

Suppose I have a particle confined between 0 and d on the x axis, and it has some wavefunction, if I measured the particle to be between some small interval [a, b], would the wavefunction collapse into a rectangle-like function with equal prob. density on the interval and zero outside? or what...

Homework Statement I'm currently writing a program that will read in a list of gaussian distributed random numbers as an array and will make a 'measurement', that is they will be assigned to another array with an associated error. This is to try and simulate the communication of Alice to Bob...

Homework Statement You measure 50V with a voltmeter, which has 300V as the max. input voltage. What will be the relative error (h%) of the measurement? Homework Equations The Attempt at a Solution hi i divided 50v / 300 V and get = 1,66 and divided it by 100 to get relative error...

Hi, Homework Statement We ran an experiment for confirming the linearity of Faraday's Law (the relation between EMF and the rate of change of flux), by plugging a magnet to a motor rotating in the axis of a solenoid (inductor). In my graph of the amplitude of EMF wrt time, I noticed some...

It is proposed to use a katharometer to mesaure the amount (about 5%) of oxygen in nitrogen, in the presence of a small amount (0.5%) hydrogen. How constant would the proportion of hydrogen have to be in order to limit errors in measurement of % oxygen to +/- 0.1%? The thermal conductivities...

Hello. I was just wandering if anyone could help. I've been doing a couple of statistics questions, and when they ask for some questions, I am not sure if I have an appropriate understanding of what the right answer should be. I would really like to understand this material, so what I want to...

Hi everybody. I have a quick question regarding the relationship between the uncertainty principle and the measurement postulate. According to the former, the higher our certainty is about the position of a particle, the lower our certainty is regarding its momentum, and vice versa. This...

Although it is well known that a series of individual photons will build up an interference pattern in a double slit setup, there have been few (if any) experiments where such a pattern is built up by sending photons through one at a time. Here is a great experiment from one of the top quantum...

Homework Statement I have to design a scale to weigh something under 1kg and all am given is a yard stick, 10 ft of fishing line, a 500g known standard mass, and a protractor. Use an angle measurement for weight. Don't just balance weights on a see-saw Homework Equations - The...

Homework Statement I have attached the photo of the circuit. My doubt in the circuit is that, I could not exactly figure out what the diodes do. The description says it is used to set the input of the op-amp to 1.6V above v-. But how exactly does it achieve that? Can somebody show it...

I apologize in advance if this has been asked many before, but I didn't see anything that answered my question on the first page of threads. Take, for example, an isolated subatomic particle which breaks down into two entangled particles. From what I've read, each of these two particles...

Hello, I was viewing a lecture of one of the professor's most possibly in MIT who demonstrated in the class room, by calling a boy and measuring him, while standing, a certain measurement say 5 ft. After that he asked the boy to lie down and again measured him and found that there is a...

I have been going through the following interesting paper on the foundations of Quantum Mechanics: http://arxiv.org/pdf/0911.0695v1.pdf 'We define the state of a system as that mathematical object from which one can determine the probability for any conceivable measurement. Physical theories can...

Author: Glenn F. Knoll Title: Radiation Detection and Measurement Amazon Link: https://www.amazon.com/dp/0470131489/?tag=pfamazon01-20 Prerequisities: Sophomore (2nd year uni) level courses in modern physics and EM, mathematics through differential equations, Level: Undergraduate...

Do you believe that "conscious" observation has anything to do with "collapsing" superimposed quantum states, or do you simply believe that interaction with a macroscopic, or sufficiently large system, is what causes superimposed quantum states to collapse? Why?

I want to measure ac voltage raging from 60v to 300v using microcontroller i have figured everything else out except how can i use 220v transformer(to step down the voltage to measure) when input is 300v one solution is to use simple resistors based potential divider to attenuate 300v to 220v...

Homework Statement This really is not a homework problem but I am studying for the qualifying exam upcoming. I came across an objective that I am not familiar with. I'm given a wave function made of a linear combination of spherical harmonics with complex coefficients. I'm asked to...

Homework Statement Spin-1 Particles prepared in the state: $$ |\psi> = \frac{2}{\sqrt29} |1> + \frac{i 3}{\sqrt29}|0> - \frac{4}{\sqrt29} |-1> $$ Where I'm guessing the ## |#> ## represents the spin state of -1,0 or 1. I'm looking to find the results of a measurements of the ## S_x ##...

Hi all, Just have a quick question regarding the measurement of vapor pressure. Firstly, let me explain my scenario. I am carrying-out some measurements of steam condensation in a vacuum. The steam is being condensed in a air-cooled heat exchanger. Initially, I let in a quantity of steam...

Hello. To give some more information on what I am to use this for: I have two signals. Both are periodic sine waves with the same frequency, but with a constant phase difference. Let's call one of the signals for ref (reference) and the other sig (signal). They can look like this: ref(t)...

Homework Statement Mercury is poured into a U tube. The left arm of the tube has a cross sectional area A_1 of 10 cm^2 and the right arm has a cross sectional area A_2 of 5 cm^2. One hundred grams of water are then poured into the right arm of the tube. A: Determine the length of the...

We recently had a long thread https://www.physicsforums.com/showthread.php?t=666861 about cases where raising and lowering indices isn't completely natural, i.e., where a vector "naturally" wants to be upper-index or lower-index. If you have a metric, then it's pretty clear to me what...

Hello, I recently read some texts which says that in a SINGLE measurement you can measure position and momentum to an arbitrary accuracy, assuring that that's not what HUB talks about. That confuses me, because I learned that HUB is there NOT simply because some property of QM prevents us...

I have been wondering what type of measurement is used to measure the space inside of a four dimensional (space, not time) object. For example, a one dimensional line's distance gets measured, a two dimensional object's area gets measured, and a three dimensional object's volume gets measured...

Light years-I just don't understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldn't they view the distance of let's say stars very differently because it...

Homework Statement I'm struggling with this, I have series of data for the deflection of a cantilever beam and the corresponding output voltages from a strain gauge, wheatstone bridge and amplifier circuit. I'm trying to find the relation between voltage output and force, i.e. Force = K x...

http://www.spacedaily.com/reports/Chinese_scientists_find_evidence_for_speed_of_gravity_999.html Done by the Institute of Geophysics at the Chinese Academy of Sciences using Earth tide measurements. The conclusion is that it is the speed of light. http://en.wikipedia.org/wiki/Earth_tide...

Hi everyone, This is really annoying me, so, I am aware of the story why oxygen was replaced with carbon-12, (because chemists were using natural occurring oxygen which was a mix of oxygen-16,17,18 and therefor was an avg?, but physicists wanted pure, isolated oxygen-16 so there was two...