# Tag Info

## Hot answers tagged experimental-physics

9

100 cN.m are 1 N.m The c before the N.m is pronounced centi. It's a standard SI prefix. 1 c of a unit is $\frac{1}{100}$ of a unit. Therefore to convert toN.m you need to multiply cN.m with 0.01. $$0.01 \text{N.m} = 1 \text{cN.m} =1 \text{N.cm}$$ Probably the prefix centi is most commonly encounter used in centimeter cm. Regarding the uses of cN.m or ...

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All EM radiation from a point source falls off in intensity with the square of the distance. LEDs can't magically change this basic physics. LEDs can be quite directional in their emission pattern. One possibility is that the orientation of the LED relative to the receiver wasn't exactly the same in all your measurements. Another is that you were fairly ...

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I assume that the person you are referring to is Felix Baumgartner, who achieved a maximum speed of Mach 1.25. While this speed is very fast, this is nowhere near the speeds achieved by meteorites, satellites, or various space junk. The space shuttle, when it was in operation, reentered the atmosphere between Mach 10 to Mach 25, which would destroy both ...

5

Electric turbine engines First off, "electric turbine engines" don't really exist. What you're probably thinking of is an electric version of the jet turbine engine, which is a type of combustion engine (it burns fuel). Air is sucked in the front, compressed by a compressor, then mixed with fuel and burned in a combustion section. A turbine ...

5

The easiest way to vaporize a metal is to create a filament of the metal. Heat the filament in the vacuum to its sublimation (vaporization) temperature. Alternatively, when the metal cannot be shaped into a filament, the metal can be encased in or painted on a "wrapper" metal. Commercial evaporators for alkali metals are designed this way. The wrapper is a ...

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Making a nozzle with that long and thin of a hole is not feasible, but you could make a larger hole behind it and just have the last 3mm be 0.6mm in diameter. This would be feasible in a ceramic, but due to cost, I might make the nozzle into an insert that goes into a larger piece made of cheaper material. Things to be concerned with: Stream breakup due to ...

4

For a detailed explanation search WikiPedia for derivative, partial derivative and total derivative. For a short, non-mathematical, summary see below. The partial derivative of a function of several variables is it's derivative with respect to one of those variables, assuming that all other variables are constant. The total derivative does not make this ...

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If you want a quick and somewhat inaccurate hill-billy engineering answer, I would take a digital kitchen scale and place the PSV ontop of it, tare it, then load up a program to test the buttons (game, menu, etc). with the scale device zero'd out, slowly depress the button until it is read by the program. a full actuation can and will differ from the ...

4

There are far too many factors involved to definitively state that a table fan cools more than a ceiling fan or vice versa. For starters, there are different styles of both. It also depends highly on what you consider "cools better". For example, if you were to come inside and are sweaty, and are looking to cool down quickly, standing in front of a small ...

4

The short answer is, anyone can make graphene, but knowing you did or doing anything with it requires a bit more equipment. I work with people who work with graphene. This is not the only way to make graphene, but it is how they do it. They use Scotch tape to pull apart graphite crystals repeatedly. Then the Scotch tape with lots of little flakes gets ...

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The difference is in the assumptions. The first "shear stress" is simply assuming the stress is uniform over the cross section. As a result, we see a shearing force $P$ shearing a rod of uniform cross section $A$, and due to the assumption or uniform shear stress across the cross section, we have the resulting $\frac{P}{A}$ shear stress. When we abandon ...

4

First Part Simplifying the $$1 \ lbf = 1 \ slug .ft/sec^2$$ then $$1 \ lbf \ sec^2 / in^4 = 1 \ (slug .ft/sec^2 ). (sec^2/in^4) = 12 \ slug /in^3$$ $$12 \ slug / in^3 * (14.6 kg / 1\ slug)*(in/25.4 \ mm)^3 = 0.0107 \ kg/mm^3$$ Note that that each slug equals to 14.6 kg so (1 slug / 14.6 kg) equals to 1.0 and any expression multiplied with 1.0 will ...

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Illustration following up from the comments We used vacuum to hold the ball bearing being dropped, from above. The ball was hand placed up against the output port of a manifold. Around it was open air. The port holding the ball connected to COMMON port of a 3/2 solenoid valve. NC to vacuum regulator, NO vent to atmosphere. When valve vented the output, part ...

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I've seen similar action when a straw is in a glass of soda. Bubbles form on the straw, causing it to "float" upwards, then the bubbles break free and the straw sinks again. Rinse, lather, repeat. In both scenarios what we're seeing is the slow release of CO2 from dissolved to gas-bubble phase. Similarly, opening a bottle of soda doesn't cause ...

3

It will depend on the degree of ionization you require, as well as the pressure of the air passing through the ionization region. Your gas will not likely be at STP if the air is moving through a reducing tunnel. Ionization and breakdown (the common name for the process of forming a plasma by ionization) occurs more easily at lower pressures (so a quickly ...

3

Like anyone who has used a compass knows, earth's magnetic field does exert a force on magnetic objects. In theory this force could be harnessed to do work, but in practice it is too small to be a concern. For example, a 1 meter long wire carrying 1 amp of current sitting perpendicular to earth's magnetic field will be subject to about 0.0001 Newtons of ...

2

Superhydrophobic surfaces generally consist of a series of micro/nano scale pillars that increase the contact angle of water on the surface. Larger contact angle means water forms more spherical drops and can roll off more easily. Changing the chemical properties of the surface layer can also help change the contact angle. These surfaces are optimized to ...

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The only major difference the alcohol choice will make is the ionization energy. While the ionization energy for Methanol is 10.85 (source), ethanol is 10.62 eV, while Isopropyl is only 10.10 eV. The slight difference will allow for more molecules at the lower potential to be ionized, making for slightly longer trails. However, this shouldn't be a major ...

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A fairly straightforward way to do this is to have the sample spring connected via a mechanical linkage to a device which traces a line on a moving spool or drum using ink on paper or similar. These sorts of paper trace devices were used until relatively recently for all kinds of devices to measure some variable over time, barometers like this are very ...

2

In general, if the calculation is multiplication by a constant, then you multiply the uncertainty by the same constant. That's assuming that "uncertainty" refers to something like standard deviation, rather than to variance: if it's variance, then you multiply by the square of the constant. If it's addition of a constant, it doesn't change the uncertainty. ...

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There are two simple options for the bearing The first is to suspend the bob from a flexible cord passing through a fairly tight grommet so it will maintain a constant point of contact in all directions. Another option is to get a large ball bearing, ideally plastic or unhardened (or at least not through hardened) steel and then drill and tap it for an ...

2

As Olin mentioned, the emission pattern is quite anisotropic. It depends on the LED. Most have primary lenses which all have unique emission patterns. One example of such can be seen in the Cree X-Lamp XP-G Datasheet (p.10) Cree® XLamp® XP-G LEDs On the left is the 'typical emission pattern' given by the manufacturer. On the right is the type of LED I'm ...

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As Olin said, LEDs, even without their lens cap, are quite directional. If you want a decent point source, the typical approach is to use an external lens to refocus the LED output as best you can onto a pinhole (20 microns if possible). This will cause some light loss but the output of the pinhole should be much closer to an ideal point source.

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What you need is a block-and-tackle, namely a gun-tackle. Source The general trick to determine advantage is how many verticals you have bearing the load (other than the end you are pulling from). Also, it must be a single rope that loops around the block. So, for example, a tackle with an advantage of 4 (or 0.25) is: Source

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If I'm understanding your question correctly, you are asking how you can build a functional laser interferometer. That is a pretty complex topic and impossible to cover in detail in a single answer. I'll however point you to Sam's laser FAQ, which is an excellent resource and has a few thoughts about building such from a CD-ROM drive: http://www.repairfaq....

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Edit: Added the requested drawing + corrected formulae for the 4 bar setup As Carl Witthoft mentioned, the buoyancy force $F_1$ from the block is proportional to the submerged/displaced volume ($V_{sub}$). $$F_1=\rho gV_{sub}$$ Let's the distance between the Arm A pivot and the intersection of Arms A and B be $d_3$ Summing the moments around Pivot A (for ...

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If I understand that picture correctly, the brightness is a function of how many subpixels are turned ON in a given image frame. Your eye integrates all the photons it receives, so if all 16 red subpixels are ON, you'll perceive "red" but also perceive "very bright." If only one is ON, you still perceive "red" but will see &...

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you do not need a CVD system to deposit metals, a planar magnetron sputtering system is more suitable. But for layers of order ~1mm in thickness you would be better off with an electroplating process.

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The simplest way to achieve this in my mind, is with two gears - one should have a drum attached with the rope wound around, and the other has the arm attached. One benefit of this method, is that you can have the gears sized such that pulling the string a long way causes the output arm to rotate more slowly than the input gear - this will give you more ...

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