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7

No, this is not classed as a "short-circuit". This is a circuit with a designed current flow - ie a 60 to 150A range is common... A "short-circuit" is a circuit where the current flow is not following the designed current path ie it is taking a "shorter" route to ground.


5

The answer to this question is complicated since the flow is fundamentally different. When supersonic flow hits a wedge it is abruptly turned by one oblique shock. After this all streamlines are parallel since in this 2D-flow-scenario the geometry/flow-area does not change anymore. When supersonic flow (think of a stream tube/cylinder) hits a cone a ...


4

Build two tables. The outer table will have a hole in the middle and only hold the glass plate. There should be about 10 cm of free space between the tables. The train will be placed on the inner table: ================== <-- glass plate || ______ || || || || || <-- train platform || || || || This way people won't bump the ...


4

UPS has, or at least had when I was transit testing packaged products, a specific packaging test standard based on ISTA standards and ASTM D4169. There's also a MIL-STD, 810 something, but I don't remember the exact number. Typically, for a parcel carrier, the test, regardless of standard, consists of environmental conditioning, a "10 pt" drop test and a ...


4

When I have received fragile content in the past it has always come with a Shockwatch label attached to the side. I'm not 100% sure, but I believe there is some sort of guarantee by the shipper to keep the forces below the level registered by the label (a guarantee which most certainly comes at added cost). Looking up the specs in the link above, these ...


4

The first design that comes to mind is a pneumatic cylinder with a large one-way valve and a slow two-way release on the back end. I've attached quick sketch below: The idea here is that the big valve on top can let air in freely - letting the device extend with little resistance. Pushing the piston back in, however, the large valve closes, forcing air out ...


3

Door closer is a great mechanism - at it's heart is a dashpot - and a check valve. If you have a check valve in parallel to the dashpot, that accomplishes the desired function. Watch below: This is your mechanism at rest. You could add a spring to the top of the dashpot to force it to go back to the fully closed state when finished - but that would ...


2

For car exidents there is a meassure, which is called Head Injury Criterion. It is a measure to estimate the possibility of an head injury during a car accident. The HIC for the time interval $t_1,t_2$ is given by $$HIC_{t_1,t_2} = (t_2-t_1)^{-1.5}\int_{t_1}^{t_2}a(t)dt.$$ The final HIC is given by the maximum value of the previuos expression, which can ...


2

it depends on how far your steal drop table travels after hitting the sample, the less travel the greater g. The kinetic energy of the drop table when it hits the sample is $$KE=1/2mv^2 \quad and\ v=\sqrt{2gh} $$ But depending on the softness or hardness of your sample and the apparatus and your weight the force of collision changes. $$F_{impact}X_{...


2

I think this is more a comment than an answer, but I have too small reputation to comment (poor me!). Summarizing, you are asking: how dynamic loads propagate inside a structure? I would underline that, in my perspective, telling that you are not concerned about vibrations, is a wrong starting point (fatigue crack derives exactly from them); for a ...


2

Here is a simple design as a starting point for you to modify according to what are your constraints and what are the data that you need to collect. On the track of the wheel, there is a graduated scale that could be fit with acceleration sensors or what not.


2

In the section "The Multiple DOF System" the Comsol document says It has been assumed that the mass matrix normalization of the eigenmodes is used and that the damping matrix can be diagonalized by the eigenmodes. Eigenvectors are assumed to be mass normalized in any mathematical derivation using them, unless somebody wants to be deliberately ...


1

Your static deflection is way too low. let's consider a 1-inch length of your angle for a basic check. Assuming steel E=29000ksi $$I=1*0.38^3/12=0.00457 in^4 $$ $\delta = \frac{wL^3}{(3EI)} = \frac{11760*1^3}{3EI}=0.0295 in$ Therefore $$ p = p_s\left(1+\sqrt{1+\frac{2h}{y}}\right) =11760(1+\sqrt{1+\frac{2*0.5}{0.0295}}=11760(1+6.899)=92786 psi \ \text{no ...


1

No, look at it this way: you are removing material that would otherwise help break the fall. All it does is give the mass a chance to penetrate deeper into the drop pad. It would be ok if you add it to existing pad for a thicker pad if you are looking for less noise and less stress to the floor.


1

If all three things labeled "joint" in your drawing are hinges, I don't think the spring will do anything at all. You don't say what you are trying to measure here, but the design doesn't seem to support the wheel properly. For example what happens it the wheel "gets stuck" in a depression? It looks like the linkages will just twist, and leave the wheel "...


1

How much money do you have? You could buy, for example, an air-suspension table such as those sold for optical lab work. You could make the table out of half-inch forged iron and bolt it thru the floor to the foundation, and then isolate the train/track setup with some rubber pads. But if you want a "sensible" coffeetable and don't want to mortgage your ...


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