How Do You Convert CFM to Thrust?

[addzkebabs]

Hey guys! I'm new to the forums here and was after some help for something that I am currently working on. I need help converting cfm to thrust, i have found the formula though i can't get my head around it.

Here it is:

CFM = Cubic Feet per Minute = Volumetric Flow Rate

Mass Flow Rate = (Density) x (Volumetric Flow Rate)

Newton’s Second Law of Motion: Force = (Mass) x (Acceleration), or F = ma

F = ma = (Mass Flow Rate) x (Velocity), given a constant flow velocity
(i.e., constant propeller speed and pitch angle).

Velocity = (Volumetric Flow Rate) / (Area), where Area = (Pi) x (r^2), the
length of a propeller blade is a good approximation for the radius, r.

Thrust = (Density) x (CFM^2) / ((Pi) x (r^2))


The amount of cfm i need to convert is 2750cfm. Any pointers?

Cheers, Addz.

 

[addzkebabs]

Ummm... to be a bit more specific I'm having trouble with this segment:

Area = (Pi) x (r^2)

What is r^2?

Although most likely dead simple for you guys, it isn't for me so don't kill me lol! (I'm really new to all of this so thanks)

Cheers, Addz.