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    mtimetraveller

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    [–] How N95 face masks work to block the particles and viruses mtimetraveller 1 points ago * (lasted edited 16 hours ago) in educationalgifs

    The overarching goal of an N95 mask is instead to get an airborne particle to touch a fiber in the mask. Regardless of how big an airborne particle is, once it touches a fiber, it stays stuck to it and doesn’t become airborne again. And so N95 masks use a bunch of different clever physics and mechanical tricks to get particles to touch their fibers.

    Particles larger than a thousandth of a millimeter basically travel in straight lines, because of their inertia. And because there are so many layers of fibers, their straight line paths are essentially guaranteed to hit a fiber and stick. Airborne particles that are really really small are so light that collisions with air molecules literally bounce them around, so they move in a random zig-zag pattern known as Brownian motion. This zig-zagging also makes it super likely that a particle will bump into a fiber and get stuck.

    Particles of in-between sizes are the hardest to filter. That’s because they don’t travel in straight lines, and they also don’t bounce around randomly. Instead, they’re carried along with the air as it flows around fibers, meaning they’re likely to get carried past fibers and sneak through even a mask with many layers. But N95 masks have a final trick up their sleeve. They can attract particles of all sizes to them using an electric field. In the presence of an electric field even neutral particles develop an internal electrical imbalance which attracts them to the source of the field. This is why neutrally-charged styrofoam sticks to an abused cat - I mean, a cat whose fur has been charged with static electricity. And that's how static electricity helps N95 mask fibers attract all particles. But unlike a cat’s fur, an N95 mask’s electric field isn’t just ordinary static electricity. Their fibers are like permanent magnets, but for electricity: electrets! Just like you can permanently magnetize a piece of iron by putting it in a strong enough magnetic field, you can ‘electretize’ a piece of plastic to give it a permanent electric field. By electretizing the fibers in an N95 mask, they gain a long-lasting ability to attract particles, which means they capture about 10 times as many particles as regular fibers. And this is, after all, the point of an N95 mask: filter out particles from the air.

    By taking advantage of the molecular scale stickiness of matter, using many layers of fibers that catch straight-moving large particles as well as zig-zagging small particles, and having an electric field that attracts all particles, you get a mask - not a strainer - that’s really good at trapping both small and large particles, and does a reasonably good job at filtering out middle sized particles.

    Precisely what fraction of those sneaky medium-sized particles get blocked gives you the number of the mask - if at least 95% of those particles are filtered out, then the mask is rated N95. Ok, so N95 masks can be very effective. But if you’re a healthcare worker wearing one of them, here are a few important things to look out for.

    The biggest influence on the performance of an N95 mask isn’t actually the mask - it's whether you wear it properly. If a mask isn’t fully sealed on your face, air (& particles you’re trying to filter) can just bypass the filter entirely. Dust, smoke, pollen, bacteria, and viruses all have different sizes, and so are filtered by N95 masks to different extents. However, germs for airborne illnesses don’t usually travel on their own – we breathe or cough them out in droplets which have a wide range of sizes. So the size of the virus or bacteria itself isn’t particularly relevant. N95 masks are intended to be disposable, but the demand from COVID-19 has led to a global shortage of N95 masks and the reality is that health workers have to reuse them - and thus decontaminate them. It’s important to be aware that certain kinds of decontamination (for example, using alcohol or liquids) can damage the electrostatic properties of a mask and destroy their filtering ability, even if the mask appears visually unaffected.

    Source: The Astounding Physics of N95 Masks

    [–] How Is The Energy Generated In Tidal Lagoon Power Plant mtimetraveller 1 points ago in educationalgifs

    A tidal lagoon is a power station that generates electricity from the natural rise and fall of the tides. Tidal lagoons work in a similar way to tidal barrages by capturing a large volume of water behind a man-made structure which is then released to drive turbines and generate electricity. Unlike a barrage, where the structure spans an entire river estuary in a straight line, a tidal lagoon encloses an area of coastline with a high tidal range behind a breakwater, with a footprint carefully designed for the local environment.

    As the tide comes in (floods) the water is held back by the turbine wicket gates, which are used to control flow through the turbine and can be completely closed to stop water entering the lagoon.  This creates a difference in water level height (head) between the inside of the lagoon and the sea. Once the difference between water levels is optimised, the wicket gates are opened and water rushes into the lagoon through the bulb turbines mounted inside concrete turbine housings in a section of the breakwater wall. As the water turns the turbines, electricity is generated.

    The water in the lagoon then returns to closely match the same level as the sea outside.  This process also happens in reverse as the tide flows out (ebbs) because the turbines are ‘bi-directional’ and so electricity can be generated from the incoming and outgoing tides.  We can hold the tide within the lagoon for approximately 2.5 hours as the sea outside ebbs and the head builds.

    As the tides rise and fall naturally, with no requirement for fuel, tidal power is truly renewable and, unlike other forms of renewable energy, is entirely predictable.  As there are always two high and two low tides every day, tidal lagoons will generate electricity over four periods a day, every day of the year. If the tides are held for 2.5 hours four times a day, it can generate power for up to 14 in every 24 hours.  The height and time of the tides can be predicted years in advance to a high degree of accuracy, allowing the precise operation of the lagoon on each tidal cycle to be optimised well in advance.

    Source: Tidal Lagoon

    [–] Not all heroes wear capes mtimetraveller 2 points ago in wholesomememes

    Well, not much. But I've donated locally to needy ones impacted by current COVID-19 lockdown.

    [–] Not all heroes wear capes mtimetraveller 2 points ago in wholesomememes

    Damn, this is nice. Any other ideas/suggestions?

    [–] Not all heroes wear capes mtimetraveller 184 points ago in wholesomememes

    Okay, I was planning to do similar on Reddit. Now, guess, I'll do on all the popular platforms. Will update soon!

    [–] Of course, NASA made this! mtimetraveller 4 points ago in ofcoursethatsathing

    Or they will lick you just to post on Tiktok!?

    [–] Neil Degrasse Tyson circa late 1970s mtimetraveller 1 points ago in OldSchoolCool

    I mean if only we had cooler astrophysicist (scientists) like this here!