Ineffectiveness per minute, per hour

[Airbrush]

The biggest blunder I always notice is when scientists use per minute (e.g. revolutions per minute) when revolutions are faster than 60 rpm. Better to call it RPS (revolutions per second) out of respect for the fact the receiver of your message may be someone who cannot easily divide and multiply mentally in order to comprehend your message. I sure cannot. Also it is ludicrous to call any speed faster than 3,600 miles per hour anything other than one mile per second (mps, or if you live outside the US, kps (kilometers per second). People can visualize a second. Few can visualize the goings-on during a minute, and probably almost nobody can visualize what can happen during an hour as unit of measure. When you say an asteroid may be moving at the speed of 50,000 miles per hour, it would be FAR better to call it "over 13 miles per SECOND" (50,000/60/60 = 13.88). Awesome to visualize what such a speed looks like!

[swansont]

There are two motivations for choice of units. One is the appropriates scale, but the other is to allow easy comparison of results, to either an experiment or a standard. One uses rpm or mph because it allows comparison with something else (e.g. a record player or engine for the former, the speed of a car for the latter)