What Are the Units for Precession Rate (Ω)?

AI Thread Summary
The precession rate, Ω, is calculated using the formula Ω = Mgr / Iω, and its units simplify to 1/(rad·s), which can be interpreted as revolutions per second. Radians are considered dimensionless in this context, allowing them to be ignored in the calculations. The period, T, is derived from Ω as T = 2π/Ω, resulting in units of seconds per revolution. There is some confusion regarding the treatment of radians, but they do not affect the dimensional analysis since they are dimensionless. Overall, the discussion clarifies the relationship between precession rate, period, and the treatment of angular measurements in calculations.
lightlightsup
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Homework Statement
The precession rate is given as ##Ω = \frac{Mgr}{Iω}##.
Relevant Equations
What are the units here?: I'm calculating it as ##\frac{1}{rad . s}##.
The precession rate is given as ##Ω = \frac{Mgr}{Iω}##.
What are the units here?: I'm calculating it as ##\frac{1}{rad . s}##.
Am I supposed to interpret this as revolutions per second, sort of like frequency, and ignore the ##rad##?
Also, period is calculated as: ##T = \frac{2π}{Ω}##. So, ##T##'s units are ##\frac{s}{rev}##?
I'm guessing that I don't quite understand yet how ##rads## are ignored in the calculations.
Edit: This refers to gyroscopic precession wherein gravity is the only force causing a torque.
 
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lightlightsup said:
Homework Statement: The precession rate is given as ##Ω = \frac{Mgr}{Iω}##.
Homework Equations: What are the units here?: I'm calculating it as ##\frac{1}{rad . s}##.
I get 1/s, which would be the same as the units for ω...

EDIT -- can you show the units you have for the first equation, and what you cancel to get your result?
 
berkeman said:
I get 1/s, which would be the same as the units for ω...

We're ignoring ##rads##, I guess? Because they are considered "dimensionless" ratios?
 
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berkeman said:
I get 1/s, which would be the same as the units for ω...

EDIT -- can you show the units you have for the first equation, and what you cancel to get your result?

##Ω =\frac{Mgr}{Iω} = \frac{kg . \frac{m}{s^2} . m}{kg.m^2.\frac{rads}{s}} = \frac{1}{rad.s} ##
##T = \frac{2π}{Ω} = \frac{\frac{2π}{rad}}{\frac{1}{rad.s}} = s##

I'm sure there is some hole in my logic here somewhere.
 
Since radians are dimensionless, don't carry them along as units. In that case, you get the correct units for Omega, IMO.
 
lightlightsup said:
##Ω =\frac{Mgr}{Iω} = \frac{kg . \frac{m}{s^2} . m}{kg.m^2.\frac{rads}{s}} = \frac{1}{rad.s} ##
##T = \frac{2π}{Ω} = \frac{\frac{2π}{rad}}{\frac{1}{rad.s}} = s##

I'm sure there is some hole in my logic here somewhere.
Over the years there have been numerous attempts to assign a dimension to angles. You can find mine at https://www.physicsforums.com/insights/can-angles-assigned-dimension/
In respect of this thread, the interesting feature is that if we write the dimensionality as Θ then Θ2=1. So 1/rads is the same as rads.
 
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