5 ms·
Dimensional analysis crimes are the best crimes. Express velocity in meter-hertz. It's wrong, but the units are right!
by chowells 3y ago
Dimensional analysis crimes are the best crimes. Express velocity in meter-hertz. It's wrong, but the units are right!
- jeffwass 3y agoOoh, you could have gone one further and done hertz-per-diopter.
- zwieback 3y agoGood point. Hertz is weird because it automatically makes one think of frequency but it's really just "per-second". I just read up about Hertz - weird he lived not that long ago. What did they use for frequency before Hertz?
- chowells 3y agoHertz are really only appropriate for describing cyclical events. But by convention the units are just 1/s, so have fun abusing it.
- diracs_stache 3y agoA period of infinity is cyclical /s
- nyanpasu64 3y agoOne interesting property of Hertz is that it's partially appropriate for describing sampling rates. I've found use in annotating separate units for "cycles/sec" and "samples/sec" so I avoid mixing them up (for example, the Nyquist rate can be expressed as 0.5 cyc/smp).
- ericbarrett 3y agoI've seen older literature that just uses "cycles," "kilocycles," and so forth. It's never abbreviated, so I always assumed the use of a named unit came from the desire to be able to write shorthand like kHz.
- billyjmc 3y agoI’ve absolutely seen it abbreviated. The wikipedia page even shows a photo of a “1000 kc” crystal resonator. https://en.wikipedia.org/wiki/Cycle_per_second https://en.wikipedia.org/wiki/Cycle_per_second
- ericbarrett 3y agoSeems annoying if you’re a physicist or RF engineer. The Hertz makes sense.
- abdullahkhalids 3y agoWe just used cycles per second (cps). Or multiples of it. Hertz was simply the name give to this unit, first in 1935, and later was included in the SI units in 1960.
- wnoise 3y agoOr measuring torque in Watt-hours (or any other unit of energy -- joules, calories, BTUs...).
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- Terr_ 3y agoObligatory comic: https://xkcd.com/687/ https://xkcd.com/687/
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- Enginerrrd 3y agoMeter-hertz is a natural expression of velocity in some contexts though. The radius of a rotating disk times the frequency of rotation would give you the tangential velocity. Or wave speed expressed as the product of wavelength and angular frequency.
- Sharlin 3y agoEquating m/s and m·Hz is perfectly correct if you're asked to calculate the linear speed of a vehicle, given the radius of its wheels and their rotation rate, assuming no slippage! This is of course equal, up to a change of frame, to the tangential speed of a point on the wheel rim, as a sibling commenter noted.
- sparkie 3y agoSome crimes can be avoided with Orientational Analysis. Nobody teaches it though.
- wnoise 3y agoWell, anyone that does geometric algebra thinks a bit about formal quantities that mix grades.