Peter,
I see what you mean. In regards to "rpm" (revolutions per minute), I think that you are correct. While in practice "rpm" can be used to measure "angular velocity" it is technically better referred to as a measure of "angular frequency" (cycles per unit of time). Thus, 1 rpm = 1 / 60 sec = 0.01667 Hz would be
correct, as shown in the Smath screen shot below, where "rpm" is, in my opinion,
correctly referred to as a unit of "frequency":
Angular frequency is, of course, directly related to angular velocity. In Smath, it would be best to convert angular frequency to angular velocity the old fashioned way:
However, regarding the built-in Smath unit "radpm", I still think this unit is defined
incorrectly. As shown in the Smath screenshot below:
In my opinion, I think the unit "radpm" should be referred to as a measure of "angular velocity"
not "frequency" in order to distinguish it from "rpm". Also, it should be defined as 1 radpm = 1 / 60 sec. If we use the same formula above but use "radpm" instead of "rad/min", Smath gives the following erroneous result:
However, redefining the unit "radpm" as 1 radpm = 1 / 60 sec allows Smath to calculate the correct result:
This could, of course, allow the user to reach incorrect results if they tried to convert "rpm" directly to "radpm" or "rad/min" using Smath's built-in unit translator. But, if we distinguish between these two units by defining "rpm" as a measure of "frequency" and "radpm" as a measure of "angular velocity", this would, as you pointed out already, be analogous to the situation between mechanical work and torque: 1Joule = 1kg*m²/s² and 1Nm = 1kg*m²/s². The user simply needs to be mindful of the distinction to avoid making an error.
Edited by user 06 July 2011 20:29:22(UTC)
| Reason: Not specified