• Wandering_Uncertainty@lemmy.world
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    8 months ago

    Because in^2 is generally said “square inches.”

    So it’s “pounds per square inch.”

    Sometimes “per” will get its own letter, like in PPM - parts per million - and sometimes it’s left off, as in PSI.

    • wieson@feddit.de
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      8 months ago

      Thanks, friend :)

      I know how it comes to be, I just think it’s stupid.

      For example, kW times h is not the same as kW per hour. That’s why kWh means kilowatt times hour.

      If I wrote ms to denote meters per second that would create massive confusion.

      • Wandering_Uncertainty@lemmy.world
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        8 months ago

        That is an excellent point. Yeah, PSI would totally read as pounds times square inches which would be something else entirely. Adding in the extra P would fix it, too. PPSI. Suppose it’s another thing that people just have to get used to, haha.

      • QuaternionsRock@lemmy.world
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        8 months ago

        Eh, it’s pretty unambiguous. kW/hour is a pretty useless unit. Power surges may be measured in kW/s or something, but they don’t really have any impact over a span of more than a couple seconds.

        Likewise, pounds times square inches is equivalent go kg*m3/s2 in SI units - which also seems pretty meaningless. Maybe there is a use for it?

        What really grinds my gears is that pounds are a unit of mass, not force. The “pounds” in “pounds per square inch” is short for “pounds-force“. It’s the force of one pound of mass accelerating at 1g. Preposterous.

      • beastlykings@sh.itjust.works
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        8 months ago

        Wait wait Wait, can you give me more on this kWh thing? I thought I understood this already.

        A single kW is a unit of power, literally 1000 watts.

        A kWh is a unit of energy, as in stored or delivered. Draw 500 watts for 2 hours? That’s a kWh. Or have a battery that can hold 1 kWh, then assuming 100% efficiency you could draw 1000 watts from it for an hour before it was empty.

        All of this is kW times hour, I would say? But in my mind I would interchangeably say per hour as well, they feel the same.

        Obviously I’m wrong, but I’d like to know why lol

        • HerrBeter@lemmy.world
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          8 months ago

          If you use exactly 20 kW for an hour, it will translate to 20 kWh. But if your power usage varies over time, you can’t keep track of it so simple. It’s just how it is.

          The unit is really watt [W] and the Greek prefix kilo (k) for 1000. This way it’s fast and easy to convert to different scales (like Mega, Giga etc) for comparing numbers