# Tag Info

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If you look at this video which claims to be a "world record spin", they claim they measured the speed (308 rpm!) with a "Sport Tach" - see for example review at http://figureskating.about.com/od/accessories/gr/sporttach.htm . Tried to follow links to their website - it seems their domain is for sale so I suspect they have gone out of business. When you ...

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If you don't want to do video, you could try with a smartphone. There are apps which can record the sensor measurements, including the accelerometer and the gyroscope. I have no idea how noisy the data will be for a skater, but if the device is firmly attached to her body close to her center of mass, it may deliver useful results. From there the sky is the ...

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In this link you can find a video analyzer tool. This tool works well with videos taken even on a smartphone, and is free and made for educational purposes. https://www.cabrillo.edu/~dbrown/tracker/ Have her hold a distinct red kerchief or ball in one hand. This way the tracker can easily track her spinning. You can get frequency as well as number of ...

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You must narrow your condition. Try measure yourself on several equipment from the same company. Choose the best spot you think that is the perfect place to measure (flat ground, nice temperature, without wind). Yes, do all the measurement on the exactly same condition. Do about 10 measurement for each equipment. By statistics, this condition will minimize ...

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I'm not sure that it makes sense to try to measure your body weight to a precision of 100 g. For example I was just thirsty and drank a 20 ounce bottle of water, which transferred about 600 g extra mass to my stomach. Even just breathing changes your mass: if you take ten half-liter breaths per minute and your exhalations contain 5% carbon dioxide by ...

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The way you quote your result should reflect your understanding of the underlying distribution. If you believe your data is normally distributed (for this you can do the Anderson-Darling normality test, for example), then taking the standard deviation and reporting mean $\pm$ standard deviation is acceptable. If you have reason to believe that the data is ...

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The most accepted way to do so is use the standard deviation, and there are several reasons for it. But to put it simply, whenever you are measuring a magnitude that "ideally" should have only one value, it is expected that the measurements will behave as a gaussian distribution. That is, the probability of getting a certain value decreases with this ...

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When we think about the state of a hydrogen atom we instinctively think about the solutions to the time independant Schrodinger equation. These are the well known atomic orbitals. However for the time independant Schrodinger equation to apply the hydrogen atom must have existed unchanged for an infinite time and it will then continue to exist unchanged for ...

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I think this is the answer, pointed out by PeterShor. Here an ironic summary from Scott Aaronson (emphasis added) We know that analog computers are not that reliable, and can go haywire because of small errors. The argument proceeds to ask why a quantum computer should be any different, since you have these amplitudes which are continuously varying ...

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It's hard to understand what exactly is being asked, so here is a first stab. I can update if further clarification is given. First, yes a quantum computer can be used to do classical calculations. In this case there will be no entanglement, and so the result is not probabilistic (except for any issues caused by decoherence, but it is assumed this is ...

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Why can't we measure the pressure at 1000 m for different temperatures? Meteorologists certainly can do that, and in fact do do that, all the time. They use weather balloons, sounding rockets, and all other kinds of instrumentation to measure conditions in the atmosphere. The resulting picture is rather complex. Conditions vary with place, the seasons, ...

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For aviation purposes, standard atmosphere is considered to be dry air at mean sea level, at 15 degrees C (59F). It is true that pressure decreases with increasing altitude, and temperature usually does, but not always. It is not a simple relationship, because it depends on humidity, heat transfer from above and below, vertical circulation, horizontal ...

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1. No, there is no "shift in meaning". "Accuracy", "precision", and "trueness" is a technical term for measurement not physics. And there is no such thing as a "measurement community" because measurement occurs everywhere. As such, "accuracy", "precision", and "trueness" are heavily overloaded technical terms used in varying fields like maths, computer ...

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The interaction is not a measurement because the probability that it will produce a measurable change in the momentum of the reflecting object is extremely small. The magnet is in a mixed state in which its momentum has a range of values that is large compared to the change in momentum produced by the force exerted by the electron. So the shift in the ...

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You're right that determining gravitational boundedness at large distances is difficult. Quick recap of the information on hand regarding the positions and velocities: Angular separation between any two galaxies Redshift Which is really not a whole lot to work with. You can't get a handle on the (projected) physical separation without knowing the ...

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The behaviour you are describing is a consequence of the virial theorem. Without going into the gory details this tells us that if some interacting system of many objects has an average total potential energy of $<U>$ then its average total kinetic energy $<T>$ is related to $<U>$ by: $$<T> = \tfrac{1}{2} <U>$$ The proof of ...

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