There is a well known video of a helicopter with 5 evenly spaced rotor blades where the rotor is synced with a digital camera's frame rate.
Assuming the camera is at 60 hertz (60 frames per second), the rotor must be spinning at x/5 * 60. Where it seems like x could be any integer. However, let's say x is 1. So the rotor is spinning at 12 hertz. It's quite possible that in actuality, it's spinning slower than that, so my equation of
rotor rate = x/5*60 seems to be incorrect.
The reason is that given the footage, it's impossible to say if a single rotor is spinning all the way around, or just 1/5, or 3/5 around, etc. Or 8/5 around.
What is the description/name of the relationship between x and 60? It's not a factor is it?
Here's the original vid: https://www.youtube.com/watch?v=yr3ngmRuGUc