physics
posted by Charles .
If gear A has 30 teeth and is spinning at 800rpm, gear B has 50 teeth and gear C has 20 teeth and gear D is spinning at 300rpm. How many teeth does gear D have?

rpms if all in a row
If any are on the same shaft. I do not have your picture.
B 800*(30/50)
C 800*(30/50)*(50/20)
D 800*(30/50)*(50/20)*(20/N) = 300
or more easily since all teeth are the same size
800*(30/N) = 300
N = 80 
B and C are on the same shaft

Now you tell me !

sorry

B = 800*30/50 = 480 rpm
so
C = 480 rpm
D = 480 (20/N) = 300
N = 32 
thank you

You are welcome :)

How exactly does Free Body Diagrams work?

Think of the body all alone in space
Add up all the force vectors on it and equate that to mass times acceleration.